Dotaz: memory a matematika okolo MemAvailable

[chtel_bych_se_zeptat]

Dobry den, kdyz chci zjistit kolik mam volne ram, kterou muzu pouzit pro spusteni novych procesu, aniz by system zacal swapovat, koukam se na hodnotu available.

Kdyz vezmu tyto informace:

free -k
              total        used        free      shared  buff/cache   available
Mem:        1874348      185836     1300484        8644      388028     1532920
Swap:        421884           0      421884

A spocitam:

1874348(total) - 185836(used) = 1688512

Co je to vlastne za cislo? Ocekaval bych ze dostanu "available", ale nadbyva me v nem nejakych 150Mb...

Predem dekuji

Odpovědi

[kolega]

Available se pocita podle tohohle patche, ktery to snad i vysvetluje:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=34e431b0ae398fc54ea69ff85ec700722c9da773

[Michal]

Linux zacne strankovat drive nez po vycerpani "available", zavisi to na nastaveni swapiness ( https://eklitzke.org/swappiness ) a mnohych dalsich faktorech (mnozstvi inactive a active neanonymni pameti, jak nove spustene aplky zatizi unreclaimable slab, kolik pameti budou sharovat,...). Je to celkove pomerne komplexni zalezitost a fundovana odpoved by vydala na dizertacni praci.

[chtel_bych_se_zeptat]

Ahoj, jasne urcite mas pravdu. To moje tvrzeni bylo velice obecne - cituju z odkazu od kolegy nahore:

+MemAvailable: An estimate of how much memory is available for starting new
+              applications, without swapping. Calculated from MemFree,
+              SReclaimable, the size of the file LRU lists, and the low
+              watermarks in each zone.
+              The estimate takes into account that the system needs some
+              page cache to function well, and that not all reclaimable
+              slab will be reclaimable, due to items being in use. The
+              impact of those factors will vary from system to system.

Nahodou odkaz na takovu dizertacni praci nemas? Nebo nejaky pekny zdroj v cestine?