Re: Beagle and logging inotify events
On Thu, Nov 15, 2007 at 08:59:46PM +0100, Jan Kara wrote: BTW: Where did this discussion started? Googling the subject gives me just one news message... Here: http://marc.info/?l=linux-fsdevelm=119499881822672w=2 and before that, here: http://marc.info/?l=gitm=119498755206826w=2 --b. - To unsubscribe from this list: send the line unsubscribe linux-fsdevel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Beagle and logging inotify events
On Wed 14-11-07 14:38:05, J. Bruce Fields wrote: On Wed, Nov 14, 2007 at 12:32:45PM -0700, Andreas Dilger wrote: On Nov 14, 2007 11:32 -0500, Chuck Lever wrote: I disagree: we don't need a bullet-proof log. We can get a significant performance improvement even with a permanent dnotify log implemented in user-space. We already have well-defined fallback behavior if such a log is missing or incomplete. The problem with a permanent inotify log is that it can become unmanageably enormous, and a performance problem to boot. Recording at that level of detail makes it more likely that the logger won't be able to keep up with file system activity. A lightweight solution gets us most of the way there, is simple to implement, and doesn't introduce many new issues. As long as it can tell us precisely where the holes are, it shouldn't be a problem. Jan Kara is working on a patch for ext4 which would store a recursive timestamp for each directory that gives the latest time that a file in that directory was modified. ZFS has a similar mechanism by virtue of doing full-tree updates during COW of all the metadata blocks and storing the most recent transaction number in each block. I suspect btrfs could do the same thing easily. That would allow recursive-descent filesystem traversal to be much more efficient because whole chunks of the filesystem tree can be ignored during scans. The problem is that people may not be happy with the random behavior of hardlinks, right? The kernel part has this non-determinism with hardlinks but it can be worked-around in userspace (and actually if you watch the whole filesystem you don't care about the non-determinism at all because you are guaranteed there is *at least one* path which indicates the file was modified). I'm planning to write a userspace library which would mostly hide the problems with hardlinks (and also problems with the fact that scanner may not have enough rights to set inode flags pointed out by Ted) from applications... Honza BTW: Where did this discussion started? Googling the subject gives me just one news message... -- Jan Kara [EMAIL PROTECTED] SUSE Labs, CR - To unsubscribe from this list: send the line unsubscribe linux-fsdevel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Beagle and logging inotify events
On Nov 13, 2007, at 7:04 PM, Jon Smirl wrote: Is it feasible to do something like this in the linux file system architecture? Beagle beats on my disk for an hour when I reboot. Of course I don't like that and I shut Beagle off. Leopard, by the way, does exactly this: it has a daemon that starts at boot time and taps FSEvents then journals file system changes to a well-known file on local disk. I don't see why this couldn't be done on Linux as well. -- Forwarded message -- From: Jon Smirl [EMAIL PROTECTED] Date: Nov 13, 2007 4:44 PM Subject: Re: Strange beagle interaction.. To: Linus Torvalds [EMAIL PROTECTED] Cc: J. Bruce Fields [EMAIL PROTECTED], Junio C Hamano [EMAIL PROTECTED], Git Mailing List [EMAIL PROTECTED], Johannes Schindelin [EMAIL PROTECTED] On 11/13/07, Linus Torvalds [EMAIL PROTECTED] wrote: On Tue, 13 Nov 2007, J. Bruce Fields wrote: Last I ran across this, I believe I found it was adding extended attributes to the file. Yeah, I just straced it and found the same thing. It's saving fingerprints and mtimes to files in the extended attributes. Things like Beagle need a guaranteed log of global inotify events. That would let them efficiently find changes made since the last time they updated their index. Right now every time Beagle starts it hasn't got a clue what has changed in the file system since it was last run. This forces Beagle to rescan the entire filesystem every time it is started. The xattrs are used as cache to reduce this load somewhat. A better solution would be for the kernel to log inotify events to disk in a manner that survives reboots. When Beagle starts it would locate its last checkpoint and then process the logged inotify events from that time forward. This inotify logging needs to be bullet proof or it will mess up your Beagle index. Logged files systems already contain the logged inotify data (in their own internal form). There's just no universal API for retrieving it in a file system independent manner. Yeah, I just turned off beagle. It looked to me like it was doing something wrongheaded. Gaah. The problem is, setting xattrs does actually change ctime. Which means that if we want to make git play nice with beagle, I guess we have to just remove the comparison of ctime. Oh, well. Git doesn't *require* it, but I like the notion of checking the inode really really carefully. But it looks like it may not be an option, because of file indexers hiding stuff behind our backs. Or we could just tell people not to run beagle on their git trees, but I suspect some people will actually *want* to. Even if it flushes their disk caches. Linus - To unsubscribe from this list: send the line unsubscribe git in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html -- Jon Smirl [EMAIL PROTECTED] -- Jon Smirl [EMAIL PROTECTED] - To unsubscribe from this list: send the line unsubscribe linux- fsdevel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html -- Chuck Lever chuck[dot]lever[at]oracle[dot]com - To unsubscribe from this list: send the line unsubscribe linux-fsdevel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Beagle and logging inotify events
On 11/14/07, Chuck Lever [EMAIL PROTECTED] wrote: On Nov 13, 2007, at 7:04 PM, Jon Smirl wrote: Is it feasible to do something like this in the linux file system architecture? Beagle beats on my disk for an hour when I reboot. Of course I don't like that and I shut Beagle off. Leopard, by the way, does exactly this: it has a daemon that starts at boot time and taps FSEvents then journals file system changes to a well-known file on local disk. Logging file systems have all of the needed info. Plus they know what is going on with rollback/replay after a crash. How about a fs API where Beagle has a token for a checkpoint, and then it can ask for a recreation of inotify events from that point forward. It's always possible for the file system to say I can't do that and trigger a full rebuild from Beagle. Daemons that aren't coordinated with the file system have a window during crash/reboot where they can get confused. Without low level support like this Beagle is forced to do a rescan on every boot. Since I crash my machine all of the time the disk load from rebooting is intolerable and I turn Beagle off. Even just turning the machine on in the morning generates an annoyingly large load on the disk. I don't see why this couldn't be done on Linux as well. -- Forwarded message -- From: Jon Smirl [EMAIL PROTECTED] Date: Nov 13, 2007 4:44 PM Subject: Re: Strange beagle interaction.. To: Linus Torvalds [EMAIL PROTECTED] Cc: J. Bruce Fields [EMAIL PROTECTED], Junio C Hamano [EMAIL PROTECTED], Git Mailing List [EMAIL PROTECTED], Johannes Schindelin [EMAIL PROTECTED] On 11/13/07, Linus Torvalds [EMAIL PROTECTED] wrote: On Tue, 13 Nov 2007, J. Bruce Fields wrote: Last I ran across this, I believe I found it was adding extended attributes to the file. Yeah, I just straced it and found the same thing. It's saving fingerprints and mtimes to files in the extended attributes. Things like Beagle need a guaranteed log of global inotify events. That would let them efficiently find changes made since the last time they updated their index. Right now every time Beagle starts it hasn't got a clue what has changed in the file system since it was last run. This forces Beagle to rescan the entire filesystem every time it is started. The xattrs are used as cache to reduce this load somewhat. A better solution would be for the kernel to log inotify events to disk in a manner that survives reboots. When Beagle starts it would locate its last checkpoint and then process the logged inotify events from that time forward. This inotify logging needs to be bullet proof or it will mess up your Beagle index. Logged files systems already contain the logged inotify data (in their own internal form). There's just no universal API for retrieving it in a file system independent manner. Yeah, I just turned off beagle. It looked to me like it was doing something wrongheaded. Gaah. The problem is, setting xattrs does actually change ctime. Which means that if we want to make git play nice with beagle, I guess we have to just remove the comparison of ctime. Oh, well. Git doesn't *require* it, but I like the notion of checking the inode really really carefully. But it looks like it may not be an option, because of file indexers hiding stuff behind our backs. Or we could just tell people not to run beagle on their git trees, but I suspect some people will actually *want* to. Even if it flushes their disk caches. Linus - To unsubscribe from this list: send the line unsubscribe git in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html -- Jon Smirl [EMAIL PROTECTED] -- Jon Smirl [EMAIL PROTECTED] - To unsubscribe from this list: send the line unsubscribe linux- fsdevel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html -- Chuck Lever chuck[dot]lever[at]oracle[dot]com -- Jon Smirl [EMAIL PROTECTED] - To unsubscribe from this list: send the line unsubscribe linux-fsdevel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Beagle and logging inotify events
Jon Smirl wrote: On 11/14/07, Chuck Lever [EMAIL PROTECTED] wrote: On Nov 13, 2007, at 7:04 PM, Jon Smirl wrote: Is it feasible to do something like this in the linux file system architecture? Beagle beats on my disk for an hour when I reboot. Of course I don't like that and I shut Beagle off. Leopard, by the way, does exactly this: it has a daemon that starts at boot time and taps FSEvents then journals file system changes to a well-known file on local disk. Logging file systems have all of the needed info. Plus they know what is going on with rollback/replay after a crash. True, but not all file systems have a journal. Consider ext2 or FAT32, both of which are still common. How about a fs API where Beagle has a token for a checkpoint, and then it can ask for a recreation of inotify events from that point forward. It's always possible for the file system to say I can't do that and trigger a full rebuild from Beagle. Daemons that aren't coordinated with the file system have a window during crash/reboot where they can get confused. A reasonably effective solution can be implemented in user space without changes to the file system APIs or implementations. IOW we already have the tools to make something useful. For example, you don't need to record every file system event to make this useful. Listing only directory-level changes (ie some file in this directory has changed) is enough to prune most of Beagle's work when it starts up. Without low level support like this Beagle is forced to do a rescan on every boot. Since I crash my machine all of the time the disk load from rebooting is intolerable and I turn Beagle off. Even just turning the machine on in the morning generates an annoyingly large load on the disk. Understood. The need is clear. My Dad's WinXP system takes 10 minutes after every start-up before it's usable, simply because the virus scanner has to check every file in the system. Same problem! I don't see why this couldn't be done on Linux as well. -- Forwarded message -- From: Jon Smirl [EMAIL PROTECTED] Date: Nov 13, 2007 4:44 PM Subject: Re: Strange beagle interaction.. To: Linus Torvalds [EMAIL PROTECTED] Cc: J. Bruce Fields [EMAIL PROTECTED], Junio C Hamano [EMAIL PROTECTED], Git Mailing List [EMAIL PROTECTED], Johannes Schindelin [EMAIL PROTECTED] On 11/13/07, Linus Torvalds [EMAIL PROTECTED] wrote: On Tue, 13 Nov 2007, J. Bruce Fields wrote: Last I ran across this, I believe I found it was adding extended attributes to the file. Yeah, I just straced it and found the same thing. It's saving fingerprints and mtimes to files in the extended attributes. Things like Beagle need a guaranteed log of global inotify events. That would let them efficiently find changes made since the last time they updated their index. Right now every time Beagle starts it hasn't got a clue what has changed in the file system since it was last run. This forces Beagle to rescan the entire filesystem every time it is started. The xattrs are used as cache to reduce this load somewhat. A better solution would be for the kernel to log inotify events to disk in a manner that survives reboots. When Beagle starts it would locate its last checkpoint and then process the logged inotify events from that time forward. This inotify logging needs to be bullet proof or it will mess up your Beagle index. Logged files systems already contain the logged inotify data (in their own internal form). There's just no universal API for retrieving it in a file system independent manner. Yeah, I just turned off beagle. It looked to me like it was doing something wrongheaded. Gaah. The problem is, setting xattrs does actually change ctime. Which means that if we want to make git play nice with beagle, I guess we have to just remove the comparison of ctime. Oh, well. Git doesn't *require* it, but I like the notion of checking the inode really really carefully. But it looks like it may not be an option, because of file indexers hiding stuff behind our backs. Or we could just tell people not to run beagle on their git trees, but I suspect some people will actually *want* to. Even if it flushes their disk caches. Linus - To unsubscribe from this list: send the line unsubscribe git in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html -- Jon Smirl [EMAIL PROTECTED] -- Jon Smirl [EMAIL PROTECTED] - To unsubscribe from this list: send the line unsubscribe linux- fsdevel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html -- Chuck Lever chuck[dot]lever[at]oracle[dot]com begin:vcard fn:Chuck Lever n:Lever;Chuck org:Oracle Corporation;Corporate Architecture: Linux Projects Group adr:;;1015 Granger Avenue;Ann Arbor;MI;48104;USA title:Principal Member of Staff tel;work:+1 248 614 5091 x-mozilla-html:FALSE version:2.1 end:vcard
Re: Beagle and logging inotify events
On 11/14/07, Chuck Lever [EMAIL PROTECTED] wrote: Jon Smirl wrote: On 11/14/07, Chuck Lever [EMAIL PROTECTED] wrote: On Nov 13, 2007, at 7:04 PM, Jon Smirl wrote: Is it feasible to do something like this in the linux file system architecture? Beagle beats on my disk for an hour when I reboot. Of course I don't like that and I shut Beagle off. Leopard, by the way, does exactly this: it has a daemon that starts at boot time and taps FSEvents then journals file system changes to a well-known file on local disk. Logging file systems have all of the needed info. Plus they know what is going on with rollback/replay after a crash. True, but not all file systems have a journal. Consider ext2 or FAT32, both of which are still common. ext2/FAT32 can use the deamon approach you describe below which also works as a short term solution. The Beagle people do have a deamon but it can be turned off. Holes where you don't record the inotify events and update the index are really bad because they can make files that you know are on the disk disappear from the index. I don't believe Beagle distinguishes between someone turning it off for a day and then turning it back on, vs a reboot. In both cases it says there was a window where untracked changes could have happened and it triggers a full rescan. The root problem here is needing a bullet proof inotify log with no windows. The only place that is going to happen is inside the file system logs. We just need an API to say recreate the inotify stream from this checkpoint forward. Things like FAT/ext2 will always return a no data available error from this API. How about a fs API where Beagle has a token for a checkpoint, and then it can ask for a recreation of inotify events from that point forward. It's always possible for the file system to say I can't do that and trigger a full rebuild from Beagle. Daemons that aren't coordinated with the file system have a window during crash/reboot where they can get confused. A reasonably effective solution can be implemented in user space without changes to the file system APIs or implementations. IOW we already have the tools to make something useful. For example, you don't need to record every file system event to make this useful. Listing only directory-level changes (ie some file in this directory has changed) is enough to prune most of Beagle's work when it starts up. Without low level support like this Beagle is forced to do a rescan on every boot. Since I crash my machine all of the time the disk load from rebooting is intolerable and I turn Beagle off. Even just turning the machine on in the morning generates an annoyingly large load on the disk. Understood. The need is clear. My Dad's WinXP system takes 10 minutes after every start-up before it's usable, simply because the virus scanner has to check every file in the system. Same problem! I don't see why this couldn't be done on Linux as well. -- Forwarded message -- From: Jon Smirl [EMAIL PROTECTED] Date: Nov 13, 2007 4:44 PM Subject: Re: Strange beagle interaction.. To: Linus Torvalds [EMAIL PROTECTED] Cc: J. Bruce Fields [EMAIL PROTECTED], Junio C Hamano [EMAIL PROTECTED], Git Mailing List [EMAIL PROTECTED], Johannes Schindelin [EMAIL PROTECTED] On 11/13/07, Linus Torvalds [EMAIL PROTECTED] wrote: On Tue, 13 Nov 2007, J. Bruce Fields wrote: Last I ran across this, I believe I found it was adding extended attributes to the file. Yeah, I just straced it and found the same thing. It's saving fingerprints and mtimes to files in the extended attributes. Things like Beagle need a guaranteed log of global inotify events. That would let them efficiently find changes made since the last time they updated their index. Right now every time Beagle starts it hasn't got a clue what has changed in the file system since it was last run. This forces Beagle to rescan the entire filesystem every time it is started. The xattrs are used as cache to reduce this load somewhat. A better solution would be for the kernel to log inotify events to disk in a manner that survives reboots. When Beagle starts it would locate its last checkpoint and then process the logged inotify events from that time forward. This inotify logging needs to be bullet proof or it will mess up your Beagle index. Logged files systems already contain the logged inotify data (in their own internal form). There's just no universal API for retrieving it in a file system independent manner. Yeah, I just turned off beagle. It looked to me like it was doing something wrongheaded. Gaah. The problem is, setting xattrs does actually change ctime. Which means that if we want to make git play nice with beagle, I guess we have to just remove the comparison of ctime. Oh, well. Git doesn't *require* it, but I like the notion of checking the inode
Re: Beagle and logging inotify events
Jon Smirl [EMAIL PROTECTED] writes: On 11/14/07, Chuck Lever [EMAIL PROTECTED] wrote: On Nov 13, 2007, at 7:04 PM, Jon Smirl wrote: Is it feasible to do something like this in the linux file system architecture? Beagle beats on my disk for an hour when I reboot. Of course I don't like that and I shut Beagle off. Leopard, by the way, does exactly this: it has a daemon that starts at boot time and taps FSEvents then journals file system changes to a well-known file on local disk. Logging file systems have all of the needed info. Actually most journaling file systems in Linux use block logging and it would be probably hard to get specific file names out of a random collection of logged blocks. And even if you could they would hit a lot of false positives since everything is rounded up to block level. With intent logging like in XFS/JFS it would be easier, but even then costly :- e.g. they might log changes to the inode but there is no back pointer to the file name short of searching the whole directory tree. -Andi - To unsubscribe from this list: send the line unsubscribe linux-fsdevel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Beagle and logging inotify events
Jon Smirl wrote: On 11/14/07, Chuck Lever [EMAIL PROTECTED] wrote: Jon Smirl wrote: On 11/14/07, Chuck Lever [EMAIL PROTECTED] wrote: On Nov 13, 2007, at 7:04 PM, Jon Smirl wrote: Is it feasible to do something like this in the linux file system architecture? Beagle beats on my disk for an hour when I reboot. Of course I don't like that and I shut Beagle off. Leopard, by the way, does exactly this: it has a daemon that starts at boot time and taps FSEvents then journals file system changes to a well-known file on local disk. Logging file systems have all of the needed info. Plus they know what is going on with rollback/replay after a crash. True, but not all file systems have a journal. Consider ext2 or FAT32, both of which are still common. ext2/FAT32 can use the deamon approach you describe below which also works as a short term solution. The Beagle people do have a deamon but it can be turned off. Holes where you don't record the inotify events and update the index are really bad because they can make files that you know are on the disk disappear from the index. I don't believe Beagle distinguishes between someone turning it off for a day and then turning it back on, vs a reboot. In both cases it says there was a window where untracked changes could have happened and it triggers a full rescan. The root problem here is needing a bullet proof inotify log with no windows. I disagree: we don't need a bullet-proof log. We can get a significant performance improvement even with a permanent dnotify log implemented in user-space. We already have well-defined fallback behavior if such a log is missing or incomplete. The problem with a permanent inotify log is that it can become unmanageably enormous, and a performance problem to boot. Recording at that level of detail makes it more likely that the logger won't be able to keep up with file system activity. A lightweight solution gets us most of the way there, is simple to implement, and doesn't introduce many new issues. As long as it can tell us precisely where the holes are, it shouldn't be a problem. The only place that is going to happen is inside the file system logs. As Andi points out, existing block-based journaling implementations won't easily provide this. And most fs journals are actually pretty limited in size. Alternately, you could insert a stackable file system layer between the VFS and the on-disk fs to provide more seamless information about updates. We just need an API to say recreate the inotify stream from this checkpoint forward. Things like FAT/ext2 will always return a no data available error from this API. How about a fs API where Beagle has a token for a checkpoint, and then it can ask for a recreation of inotify events from that point forward. It's always possible for the file system to say I can't do that and trigger a full rebuild from Beagle. Daemons that aren't coordinated with the file system have a window during crash/reboot where they can get confused. A reasonably effective solution can be implemented in user space without changes to the file system APIs or implementations. IOW we already have the tools to make something useful. For example, you don't need to record every file system event to make this useful. Listing only directory-level changes (ie some file in this directory has changed) is enough to prune most of Beagle's work when it starts up. Without low level support like this Beagle is forced to do a rescan on every boot. Since I crash my machine all of the time the disk load from rebooting is intolerable and I turn Beagle off. Even just turning the machine on in the morning generates an annoyingly large load on the disk. Understood. The need is clear. My Dad's WinXP system takes 10 minutes after every start-up before it's usable, simply because the virus scanner has to check every file in the system. Same problem! I don't see why this couldn't be done on Linux as well. -- Forwarded message -- From: Jon Smirl [EMAIL PROTECTED] Date: Nov 13, 2007 4:44 PM Subject: Re: Strange beagle interaction.. To: Linus Torvalds [EMAIL PROTECTED] Cc: J. Bruce Fields [EMAIL PROTECTED], Junio C Hamano [EMAIL PROTECTED], Git Mailing List [EMAIL PROTECTED], Johannes Schindelin [EMAIL PROTECTED] On 11/13/07, Linus Torvalds [EMAIL PROTECTED] wrote: On Tue, 13 Nov 2007, J. Bruce Fields wrote: Last I ran across this, I believe I found it was adding extended attributes to the file. Yeah, I just straced it and found the same thing. It's saving fingerprints and mtimes to files in the extended attributes. Things like Beagle need a guaranteed log of global inotify events. That would let them efficiently find changes made since the last time they updated their index. Right now every time Beagle starts it hasn't got a clue what has changed in the file system since it was last run. This forces Beagle to rescan the entire filesystem every time it is started. The
Re: Beagle and logging inotify events
On 11/14/07, Chuck Lever [EMAIL PROTECTED] wrote: Jon Smirl wrote: On 11/14/07, Chuck Lever [EMAIL PROTECTED] wrote: Jon Smirl wrote: On 11/14/07, Chuck Lever [EMAIL PROTECTED] wrote: On Nov 13, 2007, at 7:04 PM, Jon Smirl wrote: Is it feasible to do something like this in the linux file system architecture? Beagle beats on my disk for an hour when I reboot. Of course I don't like that and I shut Beagle off. Leopard, by the way, does exactly this: it has a daemon that starts at boot time and taps FSEvents then journals file system changes to a well-known file on local disk. Logging file systems have all of the needed info. Plus they know what is going on with rollback/replay after a crash. True, but not all file systems have a journal. Consider ext2 or FAT32, both of which are still common. ext2/FAT32 can use the deamon approach you describe below which also works as a short term solution. The Beagle people do have a deamon but it can be turned off. Holes where you don't record the inotify events and update the index are really bad because they can make files that you know are on the disk disappear from the index. I don't believe Beagle distinguishes between someone turning it off for a day and then turning it back on, vs a reboot. In both cases it says there was a window where untracked changes could have happened and it triggers a full rescan. The root problem here is needing a bullet proof inotify log with no windows. I disagree: we don't need a bullet-proof log. We can get a significant performance improvement even with a permanent dnotify log implemented in user-space. We already have well-defined fallback behavior if such a log is missing or incomplete. The problem with a permanent inotify log is that it can become unmanageably enormous, and a performance problem to boot. Recording at that level of detail makes it more likely that the logger won't be able to keep up with file system activity. It doesn't have to become enormous, if the checkpoint request is too old just return no-data and trigger a full scan in Beagle. 50K of log data would probably be enough. The main thing you need to cover is the reboot process and files that get touched after the beagle shuts down or before it gets started. For example the log could checkpoint once a minute, in that case you wouldn't need more than two minutes worth of log. Beagle would just remember the last checkpoint it processed and apply reapply changes after it. If someone turns Beagle off for a couple of days it should be expected that they will need a full scan when they turn it back on. A lightweight solution gets us most of the way there, is simple to implement, and doesn't introduce many new issues. As long as it can tell us precisely where the holes are, it shouldn't be a problem. The only place that is going to happen is inside the file system logs. As Andi points out, existing block-based journaling implementations won't easily provide this. And most fs journals are actually pretty limited in size. Alternately, you could insert a stackable file system layer between the VFS and the on-disk fs to provide more seamless information about updates. We just need an API to say recreate the inotify stream from this checkpoint forward. Things like FAT/ext2 will always return a no data available error from this API. How about a fs API where Beagle has a token for a checkpoint, and then it can ask for a recreation of inotify events from that point forward. It's always possible for the file system to say I can't do that and trigger a full rebuild from Beagle. Daemons that aren't coordinated with the file system have a window during crash/reboot where they can get confused. A reasonably effective solution can be implemented in user space without changes to the file system APIs or implementations. IOW we already have the tools to make something useful. For example, you don't need to record every file system event to make this useful. Listing only directory-level changes (ie some file in this directory has changed) is enough to prune most of Beagle's work when it starts up. Without low level support like this Beagle is forced to do a rescan on every boot. Since I crash my machine all of the time the disk load from rebooting is intolerable and I turn Beagle off. Even just turning the machine on in the morning generates an annoyingly large load on the disk. Understood. The need is clear. My Dad's WinXP system takes 10 minutes after every start-up before it's usable, simply because the virus scanner has to check every file in the system. Same problem! I don't see why this couldn't be done on Linux as well. -- Forwarded message -- From: Jon Smirl [EMAIL PROTECTED] Date: Nov 13, 2007 4:44 PM Subject: Re: Strange beagle interaction.. To: Linus Torvalds [EMAIL PROTECTED] Cc: J.
Re: Beagle and logging inotify events
On Wed, Nov 14, 2007 at 02:22:51PM -0500, Jon Smirl wrote: On 11/14/07, J. Bruce Fields [EMAIL PROTECTED] wrote: On Wed, Nov 14, 2007 at 04:30:16PM +0100, Andi Kleen wrote: Jon Smirl [EMAIL PROTECTED] writes: On 11/14/07, Chuck Lever [EMAIL PROTECTED] wrote: On Nov 13, 2007, at 7:04 PM, Jon Smirl wrote: Is it feasible to do something like this in the linux file system architecture? Beagle beats on my disk for an hour when I reboot. Of course I don't like that and I shut Beagle off. Leopard, by the way, does exactly this: it has a daemon that starts at boot time and taps FSEvents then journals file system changes to a well-known file on local disk. Logging file systems have all of the needed info. Actually most journaling file systems in Linux use block logging and it would be probably hard to get specific file names out of a random collection of logged blocks. And even if you could they would hit a lot of false positives since everything is rounded up to block level. With intent logging like in XFS/JFS it would be easier, but even then costly :- e.g. they might log changes to the inode but there is no back pointer to the file name short of searching the whole directory tree. So it seems the best approach given the current api's would be just to cache all the stat data, and stat every file on reboot. I don't understand why beagle is reading the entire filesystem data. I understand why even just doing the stat's could be prohibitive, though. I believe Beagle is looking at the mtimes on the files. It uses xattrs to store the last mtime it checked and then compares it to the current mtime. It also stores a hash of the file in an xattr. So even if the You meant only if, not even if? mtimes don't match it recomputes the hash and only if the hashes differ do it update its free text search index. OK, that makes a little more sense. (Though it seems unfortunate to use xattrs instead of caching the data elsewhere. Git and nfs e.g. both use the ctime to decide when a file changes, so you're invalidating their caches unnecessarily.) --b. - To unsubscribe from this list: send the line unsubscribe linux-fsdevel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Beagle and logging inotify events
On Nov 14, 2007 11:32 -0500, Chuck Lever wrote: I disagree: we don't need a bullet-proof log. We can get a significant performance improvement even with a permanent dnotify log implemented in user-space. We already have well-defined fallback behavior if such a log is missing or incomplete. The problem with a permanent inotify log is that it can become unmanageably enormous, and a performance problem to boot. Recording at that level of detail makes it more likely that the logger won't be able to keep up with file system activity. A lightweight solution gets us most of the way there, is simple to implement, and doesn't introduce many new issues. As long as it can tell us precisely where the holes are, it shouldn't be a problem. Jan Kara is working on a patch for ext4 which would store a recursive timestamp for each directory that gives the latest time that a file in that directory was modified. ZFS has a similar mechanism by virtue of doing full-tree updates during COW of all the metadata blocks and storing the most recent transaction number in each block. I suspect btrfs could do the same thing easily. That would allow recursive-descent filesystem traversal to be much more efficient because whole chunks of the filesystem tree can be ignored during scans. Cheers, Andreas -- Andreas Dilger Sr. Software Engineer, Lustre Group Sun Microsystems of Canada, Inc. - To unsubscribe from this list: send the line unsubscribe linux-fsdevel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Beagle and logging inotify events
On Wed, Nov 14, 2007 at 04:30:16PM +0100, Andi Kleen wrote: Jon Smirl [EMAIL PROTECTED] writes: On 11/14/07, Chuck Lever [EMAIL PROTECTED] wrote: On Nov 13, 2007, at 7:04 PM, Jon Smirl wrote: Is it feasible to do something like this in the linux file system architecture? Beagle beats on my disk for an hour when I reboot. Of course I don't like that and I shut Beagle off. Leopard, by the way, does exactly this: it has a daemon that starts at boot time and taps FSEvents then journals file system changes to a well-known file on local disk. Logging file systems have all of the needed info. Actually most journaling file systems in Linux use block logging and it would be probably hard to get specific file names out of a random collection of logged blocks. And even if you could they would hit a lot of false positives since everything is rounded up to block level. With intent logging like in XFS/JFS it would be easier, but even then costly :- e.g. they might log changes to the inode but there is no back pointer to the file name short of searching the whole directory tree. So it seems the best approach given the current api's would be just to cache all the stat data, and stat every file on reboot. I don't understand why beagle is reading the entire filesystem data. I understand why even just doing the stat's could be prohibitive, though. --b. - To unsubscribe from this list: send the line unsubscribe linux-fsdevel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Beagle and logging inotify events
Is it feasible to do something like this in the linux file system architecture? Beagle beats on my disk for an hour when I reboot. Of course I don't like that and I shut Beagle off. -- Forwarded message -- From: Jon Smirl [EMAIL PROTECTED] Date: Nov 13, 2007 4:44 PM Subject: Re: Strange beagle interaction.. To: Linus Torvalds [EMAIL PROTECTED] Cc: J. Bruce Fields [EMAIL PROTECTED], Junio C Hamano [EMAIL PROTECTED], Git Mailing List [EMAIL PROTECTED], Johannes Schindelin [EMAIL PROTECTED] On 11/13/07, Linus Torvalds [EMAIL PROTECTED] wrote: On Tue, 13 Nov 2007, J. Bruce Fields wrote: Last I ran across this, I believe I found it was adding extended attributes to the file. Yeah, I just straced it and found the same thing. It's saving fingerprints and mtimes to files in the extended attributes. Things like Beagle need a guaranteed log of global inotify events. That would let them efficiently find changes made since the last time they updated their index. Right now every time Beagle starts it hasn't got a clue what has changed in the file system since it was last run. This forces Beagle to rescan the entire filesystem every time it is started. The xattrs are used as cache to reduce this load somewhat. A better solution would be for the kernel to log inotify events to disk in a manner that survives reboots. When Beagle starts it would locate its last checkpoint and then process the logged inotify events from that time forward. This inotify logging needs to be bullet proof or it will mess up your Beagle index. Logged files systems already contain the logged inotify data (in their own internal form). There's just no universal API for retrieving it in a file system independent manner. Yeah, I just turned off beagle. It looked to me like it was doing something wrongheaded. Gaah. The problem is, setting xattrs does actually change ctime. Which means that if we want to make git play nice with beagle, I guess we have to just remove the comparison of ctime. Oh, well. Git doesn't *require* it, but I like the notion of checking the inode really really carefully. But it looks like it may not be an option, because of file indexers hiding stuff behind our backs. Or we could just tell people not to run beagle on their git trees, but I suspect some people will actually *want* to. Even if it flushes their disk caches. Linus - To unsubscribe from this list: send the line unsubscribe git in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html -- Jon Smirl [EMAIL PROTECTED] -- Jon Smirl [EMAIL PROTECTED] - To unsubscribe from this list: send the line unsubscribe linux-fsdevel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
