On Tue, Feb 26, 2013 at 1:57 PM, Kevin Decherf <[email protected]> wrote: > On Tue, Feb 26, 2013 at 12:26:17PM -0800, Gregory Farnum wrote: >> On Tue, Feb 26, 2013 at 11:58 AM, Kevin Decherf <[email protected]> wrote: >> > We have one folder per application (php, java, ruby). Every application has >> > small (<1M) files. The folder is mounted by only one client by default. >> > >> > In case of overload, another clients spawn to mount the same folder and >> > access the same files. >> > >> > In the following test, only one client was used to serve the >> > application (a website using wordpress). >> > >> > I made the test with strace to see the time of each IO request (strace -T >> > -e trace=file) and I noticed the same pattern: >> > >> > ... >> > [pid 4378] stat("/data/wp-includes/user.php", {st_mode=S_IFREG|0750, >> > st_size=28622, ...}) = 0 <0.033409> >> > [pid 4378] lstat("/data/wp-includes/user.php", {st_mode=S_IFREG|0750, >> > st_size=28622, ...}) = 0 <0.081642> >> > [pid 4378] open("/data/wp-includes/user.php", O_RDONLY) = 5 <0.041138> >> > [pid 4378] stat("/data/wp-includes/meta.php", {st_mode=S_IFREG|0750, >> > st_size=10896, ...}) = 0 <0.082303> >> > [pid 4378] lstat("/data/wp-includes/meta.php", {st_mode=S_IFREG|0750, >> > st_size=10896, ...}) = 0 <0.004090> >> > [pid 4378] open("/data/wp-includes/meta.php", O_RDONLY) = 5 <0.081929> >> > ... >> > >> > ~250 files were accessed for only one request (thanks Wordpress.). >> >> Okay, that is slower than I'd expect, even for an across-the-wire request... >> >> > The fs is mounted with these options: >> > rw,noatime,name=<hidden>,secret=<hidden>,nodcache. >> >> What kernel and why are you using nodcache? > > We use kernel 3.7.0. nodcache is enabled by default (we only specify user and > secretfile as mount options) and I didn't find it in the documentation of > mount.ceph. > >> Did you have problems >> without that mount option? That's forcing an MDS access for most >> operations, rather than using local data. > > Good question, I will try it (-o dcache?).
Oh right — I forgot Sage had enabled that by default; I don't recall how necessary it is. (Sage?) >> > I have a debug (debug_mds=20) log of the active mds during this test if >> > you want. >> >> Yeah, can you post it somewhere? > > Upload in progress :-) Looking forward to it. ;) -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
