• David Rientjes's avatar
    fs, seq_file: fallback to vmalloc instead of oom kill processes · 5cec38ac
    David Rientjes authored
    Since commit 058504ed ("fs/seq_file: fallback to vmalloc allocation"),
    seq_buf_alloc() falls back to vmalloc() when the kmalloc() for contiguous
    memory fails.  This was done to address order-4 slab allocations for
    reading /proc/stat on large machines and noticed because
    PAGE_ALLOC_COSTLY_ORDER < 4, so there is no infinite loop in the page
    allocator when allocating new slab for such high-order allocations.
    
    Contiguous memory isn't necessary for caller of seq_buf_alloc(), however.
    Other GFP_KERNEL high-order allocations that are <=
    PAGE_ALLOC_COSTLY_ORDER will simply loop forever in the page allocator and
    oom kill processes as a result.
    
    We don't want to kill processes so that we can allocate contiguous memory
    in situations when contiguous memory isn't necessary.
    
    This patch does the kmalloc() allocation with __GFP_NORETRY for high-order
    allocations.  This still utilizes memory compaction and direct reclaim in
    the allocation path, the only difference is that it will fail immediately
    instead of oom kill processes when out of memory.
    
    [akpm@linux-foundation.org: add comment]
    Signed-off-by: default avatarDavid Rientjes <rientjes@google.com>
    Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
    Cc: Christoph Hellwig <hch@infradead.org>
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    5cec38ac
seq_file.c 21.8 KB