On Tue, Mar 30, 2021 at 10:57:04AM +0800, Su Yue wrote: > > On Tue 23 Mar 2021 at 16:14, Ming Lei <ming.lei@xxxxxxxxxx> wrote: > > > On some ARCHs, such as aarch64, page size may be 64K, meantime there may > > be lots of CPU cores. relay_open() needs to allocate pages on each CPU > > blktrace, so easily too many pages are taken by blktrace. For example, > > on one ARM64 server: 224 CPU cores, 16G RAM, blktrace finally got > > allocated 7GB in case of 'blktrace -b 8192' which is used by > > device-mapper > > test suite[1]. This way could cause OOM easily. > > > > Fix the issue by limiting max allowed pages to be 1/8 of > > totalram_pages(). > > > > [1] https://github.com/jthornber/device-mapper-test-suite.git > > > > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> > > --- > > kernel/trace/blktrace.c | 32 ++++++++++++++++++++++++++++++++ > > 1 file changed, 32 insertions(+) > > > > diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c > > index c221e4c3f625..8403ff19d533 100644 > > --- a/kernel/trace/blktrace.c > > +++ b/kernel/trace/blktrace.c > > @@ -466,6 +466,35 @@ static void blk_trace_setup_lba(struct blk_trace > > *bt, > > } > > } > > > > +/* limit total allocated buffer size is <= 1/8 of total pages */ > > +static void validate_and_adjust_buf(struct blk_user_trace_setup *buts) > > +{ > > + unsigned buf_size = buts->buf_size; > > + unsigned buf_nr = buts->buf_nr; > > + unsigned long max_allowed_pages = totalram_pages() >> 3; > > + unsigned long req_pages = PAGE_ALIGN(buf_size * buf_nr) >> PAGE_SHIFT; > > + > > + if (req_pages * num_online_cpus() <= max_allowed_pages) > > + return; > > + > > + req_pages = DIV_ROUND_UP(max_allowed_pages, num_online_cpus()); > > + > > + if (req_pages == 0) { > > + buf_size = PAGE_SIZE; > > + buf_nr = 1; > > + } else { > > + buf_size = req_pages << PAGE_SHIFT / buf_nr; > > > Should it be: > buf_size = (req_pages << PAGE_SHIFT) / buf_nr; > ? > The priority of '<<' is lower than '/', right? :) Good catch, thanks! -- Ming
