Messages in this thread | | | Date | Sat, 5 Jan 2002 15:12:06 -0800 (PST) | From | Davide Libenzi <> | Subject | Re: 2.5.2-pre performance degradation on an old 486 (it's the scheduler) |
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On Sat, 5 Jan 2002, Mikael Pettersson wrote:
> On Sat, 5 Jan 2002 09:25:48 +0100 (CET), Matthias Hanisch wrote: > >On Sat, 5 Jan 2002, Mikael Pettersson wrote: > > > >> When running 2.5.2-pre7 on my old for-testing-only 486(*), > >> file-system accesses seem to come in distinct bursts preceded > >> by lengthy pauses. Overall performance is down quite significantly > >> compared to 2.4.18pre1 and 2.2.20pre2. To measure it I ran two > >> simple tests: > >> > >> Test 1: time to boot the kernel, from hitting enter at the LILO > >> prompt to getting a login prompt > >> Test 2: time to "rm -rf" a clean linux-2.4.17 source tree, using > >> the newly booted kernel (no other access to the tree before that, > >> so it wasn't cached in any way, and the machine was otherwise idle) > >> > >> Test 1 Test 2 > >> 2.2.21pre2: 71 sec 75 sec > >> 2.4.18pre1: 64 sec 72 sec > >> 2.5.2-pre7: 97 sec 251 sec > >> > >> I haven't noticed any slowdowns on my other boxes, so I didn't > >> do any measurements on them. On the 486 it's very very obvious. > > > >This is exactly, what I see with my old 486 box. It started with > >2.5.2-pre3, which contained two major items: > > > >- bio changes from Jens > >- scheduler changes from Davide > > > >Surprisingly, backing out the bio changes didn't help. Backing out the > >scheduler changes from Davide did!! > > BINGO! Running 2.5.2-pre8 with the scheduler changes backed out made > all the difference! Interactive responsiveness is much improved and > performance in the above two tests I ran is back to 2.4.18pre1 levels. > > With 2.5.2-pre8 vanilla the 486 is getting large variation in Test 2 > above (157s, 237s, 292s), but is never even close to 2.2/2.4 levels. > > >> (*) 100MHz 486DX4, 28MB ram, no L2 cache, two old and slow IDE disks, > >> small custom no-nonsense RedHat 7.2, kernels compiled with gcc 2.95.3.
Are you able to profile the kernel ?
- Davide
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