Messages in this thread | | | Date | Mon, 7 Jan 2002 08:32:56 +0100 | From | Jens Axboe <> | Subject | Re: [patch] 2.5.2 scheduler code for 2.4.18-pre1 ( was 2.5.2-pre performance degradation on an old 486 ) |
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On Sun, Jan 06 2002, Davide Libenzi wrote: > > Davide, > > > > If this is caused by ISA bounce problems, then you should be able to > > reproduce by doing something ala > > > > [ drivers/ide/ide-dma.c ] > > > > ide_toggle_bounce() > > { > > ... > > > > + addr = BLK_BOUNCE_ISA; > > blk_queue_bounce_limit(&drive->queue, addr); > > } > > > > pseudo-diff, just add the addr = line. Now compare performance with and > > without your scheduler changes. > > I fail to understand where the scheduler code can influence this. > There's basically nothing inside blk_queue_bounce_limit()
Eh of course not, no time will be spent inside blk_queue_bounce_limit. I don't think you looked very long at this :-)
The point is that ISA bouncing will spend some time scheduling waiting for available memory in the __GFP_DMA zone.
-- Jens Axboe
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