Messages in this thread |  | | Date | Sun, 28 Jul 2002 18:36:20 -0700 | From | Andrew Morton <> | Subject | Re: [BK PATCH 2.5] Introduce 64-bit versions of PAGE_{CACHE_,}{MASK,ALIGN} |
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William Lee Irwin III wrote: > > On Sun, Jul 28, 2002 at 05:10:48PM -0700, Andrew Morton wrote: > > - Few pages use ->private for much. Hash for it. 4(ish) bytes > > saved. > > Do you know an approximate reasonable constant of proportionality > for how many pages have ->private attached?
Well, it depends on what the mapping is using ->private for. In the case of ext2, ext3 and (soon) reiserfs mappings, ->private is only used for pagecache pages which were written to with write(2).
But for other filesystems, basically all pagecache pages have buffers at present, so I exaggerate. But as filesystems migrate to using direct-to-BIO reads, the situation gets better.
It might be useful to buffer-strip written-to pages as well, if a clean way of doing that presents itself. Maybe in refill_inactive or something.
> On Sun, Jul 28, 2002 at 05:10:48PM -0700, Andrew Morton wrote: > > - Remove the rmap chain (I just broke ptep_to_address() anyway). 4 bytes > > saved. struct page is now 20 bytes. > > How did ptep_to_address() break? I browsed over your latest changes and > missed the bit where that fell apart. I'll at least take a stab at fixing > it up until the other bits materialize.
I broke it in my five-minute thought-coding exercise. By removing page->index.
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