Date: Mon, 12 Jun 2017 07:50:23 +0800 From: Jov <amutu@amutu.com> To: "Caza, Aaron" <Aaron.Caza@ca.weatherford.com> Cc: freebsd-hackers@freebsd.org, Allan Jude <allanjude@freebsd.org> Subject: Re: FreeBSD10 Stable + ZFS + PostgreSQL + SSD performance drop < 24 hours Message-ID: <CADyrUxNeRW_fKJzoc9zoZi3J-6L%2BtXnJuW3q_4cremUy7sP7fA@mail.gmail.com> In-Reply-To: <a8523e8099404bd699525f8ff7763819@DM2PR58MB013.032d.mgd.msft.net> References: <a8523e8099404bd699525f8ff7763819@DM2PR58MB013.032d.mgd.msft.net>
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To exclude the fs problem=EF=BC=8CI will do a dd test on the pgdata data se= t after the performance drop,if the read and/or write utility can reach 100% or performance expected then I will say the problem is not fs or os. For pg,what's your output of explain analyze before and after performance drop? 2017=E5=B9=B46=E6=9C=8812=E6=97=A5 12:51 AM=EF=BC=8C"Caza, Aaron" <Aaron.Ca= za@ca.weatherford.com>=E5=86=99=E9=81=93=EF=BC=9A > Thanks Allan for the suggestions. I tried gstat -d but deletes (d/s) > doesn't seem to be it as it stays at 0 despite vfs.zfs.trim.enabled=3D1. > > This is most likely due to the "layering" I use as, for historical > reasons, I have GEOM ELI set up to essentially emulate 4k sectors > regardless of the underlying media. I do my own alignment and partition > sizing as well as have the ZFS record size set to 8k for Postgres. > > In gstat, the SSDs %busy is 90-100% on startup after reboot. Once the > performance degradation hits (<24 hours later), I'm seeing %busy at ~10%. > > #!/bin/sh > psql --username=3Dtest --password=3Dsupersecret -h /db -d test << EOL > \timing on > select count(*) from test; > \q > EOL > > Sample run of above script after reboot (before degradation hits) (Samsun= g > 850 Pros in ZFS mirror): > Timing is on. > count > ---------- > 21568508 > (1 row) > > Time: 57029.262 ms > > Sample run of above script after degradation (Samsung 850 Pros in ZFS > mirror): > Timing is on. > count > ---------- > 21568508 > (1 row) > > Time: 583595.239 ms > (Uptime ~1 day in this particular case.) > > > Any other suggestions? > > Regards, > A > > -----Original Message----- > From: owner-freebsd-hackers@freebsd.org [mailto:owner-freebsd-hackers@ > freebsd.org] On Behalf Of Allan Jude > Sent: Saturday, June 10, 2017 9:40 PM > To: freebsd-hackers@freebsd.org > Subject: [EXTERNAL] Re: FreeBSD10 Stable + ZFS + PostgreSQL + SSD > performance drop < 24 hours > > On 06/10/2017 12:36, Slawa Olhovchenkov wrote: > > On Sat, Jun 10, 2017 at 04:25:59PM +0000, Caza, Aaron wrote: > > > >> Gents, > >> > >> I'm experiencing an issue where iterating over a PostgreSQL table of > ~21.5 million rows (select count(*)) goes from ~35 seconds to ~635 second= s > on Intel 540 SSDs. This is using a FreeBSD 10 amd64 stable kernel back > from Jan 2017. SSDs are basically 2 drives in a ZFS mirrored zpool. I'm > using PostgreSQL 9.5.7. > >> > >> I've tried: > >> > >> * Using the FreeBSD10 amd64 stable kernel snapshot of May 25, > 2017. > >> > >> * Tested on half a dozen machines with different models of SSDs: > >> > >> o Intel 510s (120GB) in ZFS mirrored pair > >> > >> o Intel 520s (120GB) in ZFS mirrored pair > >> > >> o Intel 540s (120GB) in ZFS mirrored pair > >> > >> o Samsung 850 Pros (256GB) in ZFS mirrored pair > >> > >> * Using bonnie++ to remove Postgres from the equation and > performance does indeed drop. > >> > >> * Rebooting server and immediately re-running test and > performance is back to original. > >> > >> * Tried using Karl Denninger's patch from PR187594 (which took > some work to find a kernel that the FreeBSD10 patch would both apply and > compile cleanly against). > >> > >> * Tried disabling ZFS lz4 compression. > >> > >> * Ran the same test on a FreeBSD9.0 amd64 system using PostgreSQ= L > 9.1.3 with 2 Intel 520s in ZFS mirrored pair. System had 165 days uptime > and test took ~80 seconds after which I rebooted and re-ran test and was > still at ~80 seconds (older processor and memory in this system). > >> > >> I realize that there's a whole lot of info I'm not including (dmesg, > zfs-stats -a, gstat, et cetera): I'm hoping some enlightened individual > will be able to point me to a solution with only the above to go on. > > > > Just a random guess: can you try r307264 (I am mean regression in > > r307266)? > > _______________________________________________ > > freebsd-hackers@freebsd.org mailing list > > https://lists.freebsd.org/mailman/listinfo/freebsd-hackers > > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@ > freebsd.org" > > > > This sounds a bit like an issue I investigated for a customer a few month= s > ago. > > Look at gstat -d (includes DELETE operations like TRIM) > > If you see a lot of that happening, but try: vfs.zfs.trim.enabled=3D0 in > /boot/loader.conf and see if your issues go away. > > the FreeBSD TRIM code for ZFS basicallys waits until the sector has been > free for a while (to avoid doing a TRIM on a block we'll immediately > reuse), so your benchmark will run file for a little while, then suddenly > the TRIM will kick in. > > For postgres, fio, bonnie++ etc, make sure the ZFS dataset you are storin= g > the data on / benchmarking has a recordsize that matches the workload. > > If you are doing a write-only benchmark, and you see lots of reads in > gstat, you know you are having to do read/modify/write's, and that is why > your performance is so bad. > > > -- > Allan Jude > _______________________________________________ > freebsd-hackers@freebsd.org mailing list https://lists.freebsd.org/ > mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org= " > > This message may contain confidential and privileged information. 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