On Mon, Feb 22, 2016 at 09:47:58AM +0900, Sergey Senozhatsky wrote: > On (02/22/16 09:25), Minchan Kim wrote: > [..] > > I tempted it several times with same reason you pointed out. > > But my worry was that if we increase ZS_MAX_ZSPAGE_ORDER, zram can > > consume more memory because we need several pages chain to populate > > just a object. Even, at that time, we didn't have compaction scheme > > so fragmentation of object in zspage is huge pain to waste memory. > > well, the thing is -- we end up requesting less pages after all, so > zsmalloc has better chances to survive. for example, gcc5 compilation test
Indeed. I saw your test result. > > BASE > > 168 2720 0 1 115833 115831 77222 > 2 > 190 3072 0 1 109708 109707 82281 > 3 > 202 3264 0 5 1910 1895 1528 > 4 > 254 4096 0 0 380174 380174 380174 > 1 > > Total 44 285 1621495 1618234 891703 > > > PATCHED > > 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 > > Total 129 489 1627756 1618193 850147 > > > 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? > > > > Now, we have compaction facility so fragment of object might not > > be a severe problem but still painful to allocate 16 pages to store > > 3408 byte. So, if we want to increase ZS_MAX_ZSPAGE_ORDER, > > first of all, we should prepare dynamic creating of sub-page of > > zspage, I think and more smart compaction to minimize wasted memory. > > well, I agree, but given that we allocate less pages, do we really want to > introduce this complexity at this point? I agree with you. Before dynamic subpage chaining feature, we need lots of testing in heavy memory pressure with zram-swap. However, I think the feature itself is good to have in the future. :) > > -ss
