Tetsuo Handa wrote: > Tetsuo Handa wrote: > > I got OOM killers while running heavy disk I/O (extracting kernel source, > > running lxr's genxref command). (Environ: 4 CPUs / 2048MB RAM / no swap / > > XFS) > > Do you think these OOM killers reasonable? Too weak against fragmentation? > > Since I cannot establish workload that caused December 24's natural OOM > killers, I used the following stressor for generating similar situation. >
I came to feel that I am observing a different problem which is currently hidden behind the "too small to fail" memory-allocation rule. That is, tasks requesting order > 0 pages are continuously losing the competition when tasks requesting order = 0 pages dominate, for reclaimed pages are stolen by tasks requesting order = 0 pages before reclaimed pages are combined to order > 0 pages (or maybe order > 0 pages are immediately split into order = 0 pages due to tasks requesting order = 0 pages). Currently, order <= PAGE_ALLOC_COSTLY_ORDER allocations implicitly retry unless chosen by the OOM killer. Therefore, even if tasks requesting order = 2 pages lost the competition when there are tasks requesting order = 0 pages, the order = 2 allocation request is implicitly retried and therefore the OOM killer is not invoked (though there is a problem that tasks requesting order > 0 allocation will stall as long as tasks requesting order = 0 pages dominate). But this patchset introduced a limit of 16 retries. Thus, if tasks requesting order = 2 pages lost the competition for 16 times due to tasks requesting order = 0 pages, tasks requesting order = 2 pages invoke the OOM killer. To avoid the OOM killer, we need to make sure that pages reclaimed for order > 0 allocations will not be stolen by tasks requesting order = 0 allocations. Is my feeling plausible? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
