Messages in this thread | | | Subject | Re: unexpected paging during large file reads in 2.1.127 | From | Zlatko Calusic <> | Date | 18 Nov 1998 23:50:07 +0100 |
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"Stephen C. Tweedie" <sct@redhat.com> writes:
> Hi, > > On 17 Nov 1998 02:21:14 +0100, Zlatko Calusic <Zlatko.Calusic@CARNet.hr> > said: > > > "Stephen C. Tweedie" <sct@redhat.com> writes: > > >> No, we don't. We don't evict just-read-in data, because we mark such > >> pages as PG_Referenced. It takes two complete shrink_mmap() passes > >> before we can evict such pages. > > > I didn't find this in the source (in fact, add_to_page_cache clears > > PG_referenced bit, if I understood source correctly). But, see below. > > You didn't understand the source correctly. :) There is an extra > bracket you missed: > > page->flags = (page->flags & ~((1 << PG_uptodate) | (1 << PG_error))) | (1 << PG_referenced); > > We clear PG_uptodate and PG_error, but we _set_ PG_referenced.
Oops. My apologies. You're right, of course.
That makes one line in my patch superfluous.
Although I have some experience in LISP, it looks like I still have trouble counting parentheses (LISP = Lost In Stupid Parentheses). :)
Still, a small comment above that line would be extremely helpful.
> > > I must agree entirely, because with small patch you can find below, > > performance is very very good. Thanks to marking readahead pages as > > referenced, I've been able to see exact behaviour that I wanted for a > > long time. > > Excellent. >
Pleasure is all mine. :)
I mean, bits from the patch are coming exclusively from you.
I'm really looking forward to their integration in the mainstream, because performance improvement is so dramatic that I expect lots of comments on the linux-kernel list telling that "latest 2.1.xxx is so much faster".
Thanks for your good work! -- Posted by Zlatko Calusic E-mail: <Zlatko.Calusic@CARNet.hr> --------------------------------------------------------------------- "Luke... Luke... Use the MOUSE, Luke" - Obi Wan Gates
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