Messages in this thread | | | Date | Sat, 5 Jan 2002 16:16:02 +0100 (MET) | From | Mikael Pettersson <> | Subject | Re: 2.5.2-pre performance degradation on an old 486 (it's the scheduler) |
| |
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.
/Mikael - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |