On Tue, Nov 5, 2024 at 11:44 PM Usama Arif <usamaarif642@xxxxxxxxx> wrote: > > > > On 05/11/2024 09:15, Barry Song wrote: > > On Tue, Nov 5, 2024 at 9:23 PM David Hildenbrand <david@xxxxxxxxxx> wrote: > >> > >> On 05.11.24 04:40, Andrew Morton wrote: > >>> On Mon, 4 Nov 2024 13:32:55 +0100 David Hildenbrand <david@xxxxxxxxxx> wrote: > >>> > >>>>> As mentioned above, this isn't about fixing a bug; it's simply to ensure > >>>>> that swap-related metrics don't disappear. > >>>> > >>>> Documentation/process/submitting-patches.rst: > >>>> > >>>> "A Fixes: tag indicates that the patch fixes an issue in a previous > >>>> commit. It is used to make it easy to determine where a bug originated, > >>>> which can help review a bug fix." > >>>> > >>>> If there is no BUG, I'm afraid you are abusing that tag. > >>> > >>> I think the abuse is reasonable. We have no Should-be-included-with:. > >> > >> A "Belongs-to:" might make sense, for this kind of stuff that is still > >> only in an RFC. Or we update the doc to explicitly spell out this > >> special case of using "Fixes" to sort out something into the RC. > >> > >> Because if this would be already in a released kernel, it would get a > >> bit trickier: stable rules explicitly spell out "fix a real bug". > >> > >>> > >>> 0ca0c24e3211 is only in 6.12-rcX so this is the time to make > >>> userspace-visible tweaks, so the 6.12 interfaces are the same as the > >>> 6.13+ interfaces (which is what I think is happening here?) > >> > > And including the Fixes in this patch might be useful to someone who is > >>> backporting 0ca0c24e3211 into some earlier kernel for their own > >>> purposes. > >> > >> Just to be clear: adding new counters would hardly be fixing existing > >> tools that perform calculations based on existing counters. So we are > >> already changing the "userspace-visible" portion in some way, and I have > >> no idea what in vmstat we consider "stable". > >> > >> But I still don't think it's all that big of a deal except in some > >> handcrafted scenarios hardly anybody cares about; the cover letter is > >> also pretty clear on that. > > > > I may have been mistaken in the cover letter. According to the zswap data Usama > > provided for servers, zero-filled pages accounted for about 1%. > > 10% not 1% (https://lore.kernel.org/all/20240612124750.2220726-1-usamaarif642@xxxxxxxxx/). > Sorry. My memory must have faded; my mind is confused by the 1% non-zero same-page data and the 10% same-page data. Getting old :-) > > So > > really doesn't > > matter too much, but I just checked with Hailong from our team—he has data > > on same-page-filled usage in Android apps, which on average show 3-4% > > same-page-filled, with over 85% being zero-filled. Some apps even reach > > 6-7% zero-filled pages. We previously used these counters to profile > > optimizations, but with zeromap now serving as the frontend for swap files, > > those counters will disappear entirely from both zRAM and pswpin/pswpout > > metrics, as folios are filtered earlier. > > > This is what I meant in https://lore.kernel.org/all/79deed1a-9b0e-42e0-be2f-f0c3ef5fee11@xxxxxxxxx/ > when I said it affects zram as well! > > I am happy with the current version of the patch, just need the change > in Documentation/admin-guide/cgroup-v2.rst. I will update the document and send version 3 tomorrow, incorporating both your comments on "zero-filled" and David's suggestion regarding "move out of memory". > > Thanks, > Usama > > > Hailong essentially has a table that looks like the below which could be > > collected from the existing counters: > > > > com.xxx.app 5% same-page-filled. 88% zero > > com.yyy.app 6% same-page-filled. 85% zero > > com.zzz.map 6.7 same-page-filled. 88% zero > > .... > > > > Anyone on 6.12 will be unable to track zero-filled pages unless they > > backport this patch from a newer kernel version if it doesn’t make it > > into 6.12. > > > > Whether it's marked as 'Belongs-to:' or 'Fixes:', I'd prefer we aim to > > land it in > > 6.12 :-) > > > >> > >> So I'll shut up now and let people figure out the naming first, and if a > >> new counter is required at all :) > >> > >> -- > >> Cheers, > >> > >> David / dhildenb > >> > > Thanks Barry
