Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

Paul, > On Wednesday 16 November 2011 at 06:04 Dmitry Yemanov wrote: > > > Also, some > > Windows versions are suspected in giving the file system cache too > > high priority thus possibly swapping out the pages of the process > > working set, so a largish internal page cache could prove itself t

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

Hello, Dmitry! Wednesday, November 16, 2011, 9:04:18 AM, you wrote: DY> Handling memory allocation automagically may sound like a clever idea, DY> but let's don't forget that DBAs often have to set up the higher limit DY> of the resource consumption, so the cache limit is still likely to DY> per

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

> On Wednesday 16 November 2011 at 06:04 Dmitry Yemanov wrote: > >> Also, some >> Windows versions are suspected in giving the file system cache too high >> priority thus possibly swapping out the pages of the process working >> set, so a largish internal page cache could prove itself to be a bad >

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

>> Ah, this sounds interesting. So, (total fetches - adjacent fetches) >> gives me some kind of unique fetches from the cache? > > Yes, I would hope so. > >> I have a dream (*g*): Why shouldn't Firebird be able to automagically >> increase RAM usage beyond the strict pattern (page buffers * page si

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

16.11.2011 10:46, Paul Reeves wrote: > Do you know which windows versions? Here is the link that might be useful: http://blog.nashcom.de/nashcomblog.nsf/dx/new-performance-problem-with-domino-on-windows-2008-64bit.htm but the explanation there doesn't sound very realistic, IMHO. Perhaps Nickol

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

Paul Reeves [2011-11-16 07:46] : > On Wednesday 16 November 2011 at 06:04 Dmitry Yemanov wrote: > >> Also, some >> Windows versions are suspected in giving the file system cache too high >> priority thus possibly swapping out the pages of the process working >> set, so a largish internal page cac

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

On Wednesday 16 November 2011 at 06:04 Dmitry Yemanov wrote: > Also, some > Windows versions are suspected in giving the file system cache too high > priority thus possibly swapping out the pages of the process working > set, so a largish internal page cache could prove itself to be a bad > idea i

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

16.11.2011 3:16, Thomas Steinmaurer wrote: > > Ah, this sounds interesting. So, (total fetches - adjacent fetches) > gives me some kind of unique fetches from the cache? Yes, I would hope so. > I have a dream (*g*): Why shouldn't Firebird be able to automagically > increase RAM usage beyond the s

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

Hello Dmitry, >> I guess the same applies to MON$IO_STATS.MON$PAGE_FETCHES? If so, isn't >> comparing MON$PAGE_READS with MON$PAGE_FETCHES a bit misleading if one >> wants to check to possibly increase the database page buffers? > > I bet you're thinking about the "cache hit ratio" which is common

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

15.11.2011 2:11, Thomas Steinmaurer wrote: > > I guess the same applies to MON$IO_STATS.MON$PAGE_FETCHES? If so, isn't > comparing MON$PAGE_READS with MON$PAGE_FETCHES a bit misleading if one > wants to check to possibly increase the database page buffers? I bet you're thinking about the "cache hi

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

> >> PS Snapshot (concurrency) transaction guarantees that once read > >> record could be read again and will be the same. So, in theory, we > >> can just re-read same data page when looking for next record. > > > > Why "in theory"? > > Because i want to be careful and don't want to make too

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

> Vlad, > >> PS Snapshot (concurrency) transaction guarantees that once read record >> could be read again and will be the same. So, in theory, we can just >> re-read same data page when looking for next record. > > Why "in theory"? Because i want to be careful and don't want to make too ear

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

>> It would be also interesting if "reads" exposed in various places (isql, >> monitoring tables, trace api) are pure physical reads from disk and/or >> fetched from the OS file system cache. >> >> I guess, it could be also from the file system cache, because I've seen >> situations where execution

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

> It would be also interesting if "reads" exposed in various places (isql, > monitoring tables, trace api) are pure physical reads from disk and/or > fetched from the OS file system cache. > > I guess, it could be also from the file system cache, because I've seen > situations where execution t

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

Vlad, > PS Snapshot (concurrency) transaction guarantees that once read record > could be read again and will be the same. So, in theory, we can just > re-read same data page when looking for next record. Why "in theory"? I don't see how the DP could change for the purposes of the next record fo

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

>>> In your example we see 7149 physical reads and 214192 times this >>> pages was referenced by the engine. To read a record engine needs to >>> access pointer page and (at least one) data page. You have ~100K records >> so we can explain ~200K fetches. >> >> Ok, but is there a way then to t

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

> On Mon, Nov 14, 2011 at 5:11 PM, Thomas Steinmaurer > wrote: > > > Ok, but is there a way then to tell how many pages have been fetched > from the cache as the number above for fetched is more likely > "referenced" and not real number of pages fetched fr

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

> Hi Vlad, > > >>In your example we see 7149 physical reads and 214192 times this pages >> was >> referenced by the engine. To read a record engine needs to access pointer >> page and >> (at least one) data page. You have ~100K records so we can explain ~200K >> fetches. >> >> > I think that

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

On Mon, Nov 14, 2011 at 5:26 PM, Leyne, Sean wrote: > > > In your example we see 7149 physical reads and 214192 times this > > The ideal statistic that would help in knowing whether the cache needs to > be increased would be "disk re-reads", but that would require that the > engine track a li

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

Hi Vlad, >In your example we see 7149 physical reads and 214192 times this pages > was > referenced by the engine. To read a record engine needs to access pointer > page and > (at least one) data page. You have ~100K records so we can explain ~200K > fetches. > > I think that when doing an ex

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

Ann, > On Mon, Nov 14, 2011 at 4:40 PM, Thomas Steinmaurer > wrote: > > > So, the numbers I see is number of pages? > > > For reads and writes. Marks and Fetches are recorded each time a page > is referenced in cache. So if you read 20 records on a page, you'll

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

On Mon, Nov 14, 2011 at 5:11 PM, Thomas Steinmaurer wrote: > > Ok, but is there a way then to tell how many pages have been fetched > from the cache as the number above for fetched is more likely > "referenced" and not real number of pages fetched from memory? > Pages aren't fetched from cache.

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

> > In your example we see 7149 physical reads and 214192 times this > > pages was referenced by the engine. To read a record engine needs to > > access pointer page and (at least one) data page. You have ~100K records > so we can explain ~200K fetches. > > Ok, but is there a way then to tell

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

On Mon, Nov 14, 2011 at 4:40 PM, Thomas Steinmaurer wrote: > > So, the numbers I see is number of pages? > For reads and writes. Marks and Fetches are recorded each time a page is referenced in cache. So if you read 20 records on a page, you'll probably get 40 fetches - one for each reference

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

- Original Message - From: "Thomas Steinmaurer" To: "For discussion among Firebird Developers" Sent: Tuesday, November 15, 2011 12:11 AM Subject: Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...) > Hi Vlad, > >&g

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

Hi Vlad, as the subject says. What's the unit for the resulting values for number of reads, writes, fetches, marks? Just want to be sure if a particular result makes sense here. ;-) >>> >>> Same as for isql's statistics - number of operations. Note, we have no >>> operations o

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

> Hi Vlad, > >>> as the subject says. What's the unit for the resulting values for number >>> of reads, writes, fetches, marks? Just want to be sure if a particular >>> result makes sense here. ;-) >> >> Same as for isql's statistics - number of operations. Note, we have no >> operations on g

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

Hi Vlad, >> as the subject says. What's the unit for the resulting values for number >> of reads, writes, fetches, marks? Just want to be sure if a particular >> result makes sense here. ;-) > > Same as for isql's statistics - number of operations. Note, we have no > operations on group of pa

Re: [Firebird-devel] Trace API - What's the unit for number of (reads |fetches ...)

> as the subject says. What's the unit for the resulting values for number > of reads, writes, fetches, marks? Just want to be sure if a particular > result makes sense here. ;-) Same as for isql's statistics - number of operations. Note, we have no operations on group of pages, so, for ex.

[Firebird-devel] Trace API - What's the unit for number of (reads | fetches ...)

Hello, as the subject says. What's the unit for the resulting values for number of reads, writes, fetches, marks? Just want to be sure if a particular result makes sense here. ;-) Thanks, Thomas -- RSA(R) Conference 2