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17 messages in ru.sysoev.nginxRe: Cache questions| From | Sent On | Attachments |
|---|---|---|
| Jim Ohlstein | Jul 10, 2009 4:39 pm | |
| Maxim Dounin | Jul 13, 2009 4:32 am | |
| Igor Sysoev | Jul 13, 2009 4:48 am | |
| Jim Ohlstein | Jul 13, 2009 1:01 pm | |
| Igor Sysoev | Jul 13, 2009 1:17 pm | |
| Maxim Dounin | Jul 13, 2009 1:50 pm | |
| Jim Ohlstein | Jul 13, 2009 5:44 pm | |
| Maxim Dounin | Jul 13, 2009 7:29 pm | |
| Jim Ohlstein | Jul 13, 2009 8:09 pm | |
| Igor Sysoev | Jul 13, 2009 10:21 pm | |
| Jim Ohlstein | Jul 14, 2009 6:25 am | |
| Igor Sysoev | Jul 14, 2009 8:10 am | |
| Jim Ohlstein | Jul 14, 2009 8:27 am | |
| Igor Sysoev | Jul 14, 2009 8:41 am | |
| Jim Ohlstein | Jul 14, 2009 8:55 am | |
| Marcus Clyne | Jul 14, 2009 12:22 pm | |
| merlin corey | Jul 14, 2009 2:37 pm |
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| Subject: | Re: Cache questions | Actions... |
|---|---|---|
| From: | Igor Sysoev (is...@rambler-co.ru) | |
| Date: | Jul 13, 2009 1:17:23 pm | |
| List: | ru.sysoev.nginx | |
On Mon, Jul 13, 2009 at 04:02:06PM -0400, Jim Ohlstein wrote:
Igor Sysoev wrote:
On Mon, Jul 13, 2009 at 03:33:21PM +0400, Maxim Dounin wrote:
Hello!
On Fri, Jul 10, 2009 at 07:39:46PM -0400, Jim Ohlstein wrote:
I'm using the fastcgi cache for static files (images, javascript,css) and just found multiple lines in the error log like this one:
2009/07/10 10:22:54 [crit] 22476#0: ngx_slab_alloc() failed: no memory in cache keys zone "one"
So I increased the memory available for the zone and reloaded nginx. It took over five hours to go through the cache but these are the relevant entries:
2009/07/10 12:11:03 [notice] 21038#0: start cache manager process 32730 2009/07/10 12:11:04 [notice] 21038#0: cache manager process 22480 exited with code 0
and finally
2009/07/10 17:43:27 [notice] 32730#0: http file cache: /usr/local/nginx/cache 11638.289M, bsize: 4096
My questions are:
Is that simply the total (11638.289MB or 11.4GB) of all of the file sizes, or is that the actual disk space consumed taking into account total number of blocks used multiplied by the block size? The number
It's size on disk (i.e. number of blocks * block size), but for files only (it doesn't take directories into account).
Just note: nginx rounds a file size to the bsize. bsize is f_bsize from statfs() or f_frsize from statvfs(). I'm not sure that bsize matches always a filesystem allocation unit.
OK, Thanks.
In trying to tune this, if I set fastcgi_cache_min_uses to 2, does that mean that a file will only be written to the cache the second time that it is requested? Google translate did not give me a clear answer to this from the Russian documentation. I think that I could improve efficiency greatly if I didn't cache files on the first request.
Yes, a file will be cached only on the second request made during period set in by "inactive" option of fastcgi_cache_path directive.
I would know better if I could get some statistics. I know the last time I asked the answer was "not yet". Do you have any idea when this might be implemented even on a rudimentary basis?
You may log $upstream_cache_status.
could be quite different given what I estimate are nearly one million mostly small files in the cache at this point.
When I next upgrade nginx (I'm running 0.8.4), and I attempt a "graceful upgrade" will it have to go through this entire process again?
Yes. Binary upgrade doesn't preserve shared memory zones, so cache will be rescanned again.
Note that nginx uses cache even before it was completely scanned, so it shouldn't be a problem.
Yes, but it uses a fair bit of system resources scanning a large cache. Nothing much to be done about it though.
I tried to minimize impact of cache scanning according to this comment:
/* * if processing 100 files takes more than 200ms, * it seems that many operations require disk i/o, * therefore sleep 200ms */
-- Igor Sysoev http://sysoev.ru/en/