On (02/22/16 10:34), Minchan Kim wrote:
[..]
> >
> > that's 891703 - 850147 = 41556 less pages. or 162MB less memory used.
> > 41556 less pages means that zsmalloc had 41556 less chances to fail.
>
>
> Let's think swap-case which is more important for zram now. As you know,
> most of usecase are swap in embedded world.
> Do we really need 16 pages allocator for just less PAGE_SIZE objet
> at the moment which is really heavy memory pressure?
well, it's not about having less PAGE_SIZE sized objects, it's about
allocating less pages in the first place; and to achieve this we need
less PAGE_SIZE sized objects.
in the existing scheme of things (current implementation) allocating
up to 16 pages to end up using less pages looks quite ok.
and not all of the huge classes request 16 pages to become a 'normal' class:
191 3088 1 0 3588 3586 2760 10
192 3104 1 0 3740 3737 2860 13
194 3136 0 1 7215 7208 5550 10
197 3184 1 0 11151 11150 8673 7
199 3216 0 1 9310 9304 7315 11
200 3232 0 1 4731 4717 3735 15
202 3264 0 1 8400 8396 6720 4
206 3328 0 1 22064 22051 17927 13
207 3344 0 1 4884 4877 3996 9
208 3360 0 1 4420 4415 3640 14
211 3408 0 1 11250 11246 9375 5
212 3424 1 0 3344 3343 2816 16
214 3456 0 2 7345 7329 6215 11
217 3504 0 1 10801 10797 9258 6
219 3536 0 1 5295 5289 4589 13
222 3584 0 0 6008 6008 5257 7
223 3600 0 1 1530 1518 1350 15
225 3632 0 1 3519 3514 3128 8
228 3680 0 1 3990 3985 3591 9
230 3712 0 2 2167 2151 1970 10
232 3744 1 2 1848 1835 1694 11
234 3776 0 2 1404 1384 1296 12
235 3792 0 2 672 654 624 13
236 3808 1 2 615 592 574 14
238 3840 1 2 1120 1098 1050 15
254 4096 0 0 241824 241824 241824 1
hm.... I just thought about it. do we have a big enough computation
error in static int get_pages_per_zspage(int class_size)
777 zspage_size = i * PAGE_SIZE;
778 waste = zspage_size % class_size;
779 usedpc = (zspage_size - waste) * 100 / zspage_size;
780
781 if (usedpc > max_usedpc) {
782 max_usedpc = usedpc;
783 max_usedpc_order = i;
784 }
to begin `misconfiguring' the classes? we cast `usedpc' to int, so we can miss
the difference between 90% and 90.95% for example... hm, need to check it later.
so, yes, dynamic page allocation sounds interesting. but should it be part of
this patch set or we can introduce it later (I think we can do it later)?
a good testing for now would be really valuable, hopefully you guys can help
me here. depending on those tests we will have a better road map, I think.
the test I've done (and will do more) demonstrate that we save pages.
-ss
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