Date: Thu, 6 Sep 2018 01:11:30 -0700 From: Mark Millard <marklmi@yahoo.com> To: Kirk McKusick <mckusick@mckusick.com> Cc: FreeBSD Filesystems <freebsd-fs@FreeBSD.org>, bob prohaska <fbsd@www.zefox.net> Subject: Re: CFT: TRIM Consolodation on UFS/FFS filesystems Message-ID: <97765759-B81A-44F0-98A0-F7B9D05F7432@yahoo.com> In-Reply-To: <20180906001217.GB818@www.zefox.net> References: <A751682B-6718-4E9F-87DB-2C7AA7076854@yahoo.com> <201809052207.w85M7GS2000773@chez.mckusick.com> <20180906001217.GB818@www.zefox.net>
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[Just correcting a bad claim about the timing of the two buildworld runs that were referenced. It could be misleading to Kirk for his requested information.] On 2018-Sep-5, at 5:12 PM, bob prohaska <fbsd at www.zefox.net> wrote: > On Wed, Sep 05, 2018 at 03:07:16PM -0700, Kirk McKusick wrote: >>=20 >> It is a bit tricky to just turn off TRIM and then measure it, because >> in the immediate aftermath of its having been used, it will leave >> behind a legacy of easier to use flash areas yet not have the cost >> of keeping them cleaned up. So, it might initially look like enabling >> TRIM is a bad idea. Thus you would have to run many installworlds >> without TRIM enabled to see what the long-term result of not using >> TRIM turns out to be. >>=20 >=20 > Just for fun I ran a (somewhat absurd) -j4 buildworld on RPI3 using 6 = GB of swap, > three on USB and three on microSD, just to see if anything interesting = (bad) happened.=20 > The process took about 24 hours, and the oversuppy of swap didn't = cause any obvious=20 > problems. Next I turned on TRIM and re-ran the buildworld script. =20 >=20 > There were no obvious problems, but the process took about an extra = hour. buildworld did not take an hour longer for one vs. the other based on the timestamps in the log files: trim off: World build started on Sun Sep 2 20:28:12 PDT 2018 . . . World build completed on Mon Sep 3 21:35:47 PDT 2018 So somewhat over 25 hours 7 minutes. trim on: World build started on Tue Sep 4 00:02:36 PDT 2018 . . . World build completed on Wed Sep 5 01:12:47 PDT 2018 So somewhat over 25 hours 10 minutes. I get an under 5 minute difference from those timestamps. > Since /var, /tmp and /usr were all on USB there was no hope TRIM could = be > any help on the busy filesystems. TRIM was enabled on microSD, but it = had > little to do. There does seem to be a modest penalty for using TRIM = when > it can't help much. >=20 > Is there any hope of implementing something like TRIM for USB on the = Pi? > It appears that congestion on USB is a serious bottlneck from time to = time > just for traffic with /tmp and /usr. Adding swap to the mix makes it = worse. >=20 > Log files are at > http://www.zefox.net/~fbsd/rpi3/swaptests/r338342/3gbsd_3gbusb/ > in case they're of interest. =3D=3D=3D Mark Millard marklmi at yahoo.com ( dsl-only.net went away in early 2018-Mar)
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