On 2015/6/9 23:03, Catalin Marinas wrote: > On Tue, Jun 09, 2015 at 09:10:45AM +0100, Zhang, Yanmin wrote: >> On 2015/6/8 18:13, Catalin Marinas wrote: >>> As I replied already, I don't think this is that bad, or at least not >>> worse than what kmemleak already does (looking at all data whether it's >>> pointer or not). >> It depends. As for memleak, developers prefers there are false alarms instead >> of missing some leaked memory. > Lots of false positives aren't that nice, you spend a lot of time > debugging them (I've been there in the early kmemleak days). Anyway, > your use case is not about false positives vs. negatives but just false > negatives. > > My point is that there is a lot of random, pointer-like data read by > kmemleak even without this memset (e.g. thread stacks, non-pointer data > in kmalloc'ed structures, data/bss sections). Just doing this memset may > reduce the chance of false negatives a bit but I don't think it would be > noticeable. > > If there is some serious memory leak (lots of objects), they would > likely show up at some point. Even if it's a one-off leak, it's possible > that it shows up after some time (e.g. the object pointing to this > memory block is freed). > >>> It also doesn't solve the kmem_cache_alloc() case where >>> the original object size is no longer available. >> Such issue around kmem_cache_alloc() case happens only when the >> caller doesn't initialize or use the full object, so the object keeps >> old dirty data. > The kmem_cache blocks size would be aligned to a cache line, so you > still have some extra bytes never touched by the caller. > >> This patch is to resolve the redundant unused space (more than object size) >> although the full object is used by kernel. > So this solves only the cases where the original object size is still > known (e.g. kmalloc). It could also be solved by telling kmemleak the > actual object size. Your explanation is reasonable. The patch is for debug purpose. Maintainers can make decision based on balance. Xinwu is a new developer in kernel community. Accepting the patch into kernel can encourage him definitely. :) Yanmin -- 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>