Messages in this thread | | | Date | Wed, 9 Jan 2002 09:23:41 -0800 (PST) | From | "Randy.Dunlap" <> | Subject | Re: bounce buffer usage |
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On Tue, 8 Jan 2002, Jens Axboe wrote:
| On Mon, Jan 07 2002, Randy.Dunlap wrote: | > | > OK, here's 'fillmem 700' run against 5 kernels as described below, | > with my bounce io/swap statistics patch added. | > | > All tests are 6 instances of "fillmem 700" (700 MB) on a 4-way 4 GB | > x86 VA 4450 server. | > | > I'm including a reduced version of /proc/stat -- before and after the | > fillmem test in each case. | > | > Let me know if you'd like to see other variations. | | The results look very promising, although I'm a bit surprised that 2.5 | is actually that much quicker :-)
I was too. When I have the bounce accounting straightened out, I'll run each test multiple times.
| The bounce counts you are doing don't make too much sense to me though, | how come 2.4 + block-high and 2.5 show any bounced numbers at all? Maybe | you are not doing the accounting correctly? To get the right counts do | something ala:
Clearly I mucked that up. Thanks for pointing it out. The patch below makes sense, but I also want to count "bounced swap IOs" separately. I'll retest and report that when I have it done.
| +++ mm/highmem.c | @@ -409,7 +409,9 @@ | vfrom = kmap(from->bv_page) + from->bv_offset; | memcpy(vto, vfrom, to->bv_len); | kunmap(from->bv_page); | - } | + bounced_write++; | + } else | + bounced_read++; | } | | Of course those are all bounces, not just (or only) swap bounces. Also | note that the above is not SMP safe.
Is this the only place that kstat (kernel_stat) counters are not SMP safe...?
-- ~Randy
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