On Mon, Jun 08, 2015 at 06:06:59PM +0100, Catalin Marinas wrote: > The kmemleak memory scanning uses finer grained object->lock spinlocks > primarily to avoid races with the memory block freeing. However, the > pointer lookup in the rb tree requires the kmemleak_lock to be held. > This is currently done in the find_and_get_object() function for each > pointer-like location read during scanning. While this allows a low > latency on kmemleak_*() callbacks on other CPUs, the memory scanning is > slower. > > This patch moves the kmemleak_lock outside the core scan_block() > function allowing the spinlock to be acquired/released only once per > scanned memory block rather than individual pointer-like values. The > memory scanning performance is significantly improved (by an order of > magnitude on an arm64 system). > > Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > --- > > Andrew, > > While sorting out some of the kmemleak disabling races, I realised that > kmemleak scanning performance can be improved. On an arm64 system I > tested (albeit not a fast one but with 6 CPUs and 8GB of RAM), > immediately after boot an "time echo scan > /sys/kernel/debug/kmemleak" > takes on average 70 sec. With this patch applied, I get on average 4.7 > sec. I need to make a correction here as I forgot lock proving enabled in my .config when running the tests. With all the spinlock debugging disabled, I get 9.5 sec vs 3.5 sec. Still an improvement but no longer by an order of magnitude. -- Catalin -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>