On (24/06/25 15:33), Andrew Morton wrote: > On Fri, 31 May 2024 16:32:04 +0200 David Hildenbrand <david@xxxxxxxxxx> wrote: > > > On 31.05.24 16:27, Matthew Wilcox wrote: > > > On Thu, May 30, 2024 at 02:01:23PM +0900, Sergey Senozhatsky wrote: > > > 1409: 83 c0 01 add $0x1,%eax > > > if (mapcount < PAGE_MAPCOUNT_RESERVE + 1) > > > 140c: 83 f8 81 cmp $0xffffff81,%eax > > > 140f: 7d 63 jge 1474 <filemap_unaccount_folio+0x8 > > > 4> > > > if (folio_test_hugetlb(folio)) > > > 1411: 80 7b 33 84 cmpb $0x84,0x33(%rbx) > > > 1415: 74 4e je 1465 <filemap_unaccount_folio+0x75> > > > > > > so we go from "mov, and, cmp, je" to just "cmpb, je", which must surely > > > be faster to execute as well as being more compact in the I$ (6 bytes vs 15). > > > > > > Anyway, not tested but this is the patch I used to generate the above. > > > More for comment than application. > > > > Right, it's likely very similar to my previous proposal to use 8 bit > > (uint8_t) for the type. > > > > https://lore.kernel.org/all/00ba1dff-7c05-46e8-b0d9-a78ac1cfc198@xxxxxxxxxx/ > > > > I would prefer if we would do that separately; unless someone is able to > > raise why we care about zram + 256KiB that much right now. (claim: we don't) > > > > iow, "this is ok for now", yes? Perhaps. I'm not in position to claim that zram + 256KiB PAGE_SIZE is irrelevant, but I'm also not in position to claim the opposite. Matthew and David have ideas/proposals/patches to fix it should 256KiB PAGE_SIZE become an issue.
