From: Eduard Shishkin <eduard.shishkin@xxxxxxxxxx> Don't merge too many pages when composing a 9p message because: . it doesn't lead to essential performance improvement; . to not allow user space to allocate big amount of kernel memory. We use a limit of 256K (for total size of all pages merged per message), as larger values don't provide any visible speedup. Signed-off-by: Eduard Shishkin <eduard.shishkin@xxxxxxxxxx> --- fs/9p/v9fs.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/fs/9p/v9fs.c b/fs/9p/v9fs.c index 58bff9e..50a4034 100644 --- a/fs/9p/v9fs.c +++ b/fs/9p/v9fs.c @@ -319,6 +319,8 @@ void put_flush_set(struct v9fs_flush_set *fset) kfree(fset); } +#define MAX_FLUSH_DATA_SIZE (262144) + /** * Allocate and initalize flush set * Pre-conditions: valid msize is set @@ -333,6 +335,11 @@ int alloc_init_flush_set(struct v9fs_session_info *v9ses) if (num_pages < 2) /* speedup impossible */ return 0; + if (num_pages > (MAX_FLUSH_DATA_SIZE >> PAGE_SHIFT)) + /* + * no performance gain with larger values + */ + num_pages = MAX_FLUSH_DATA_SIZE >> PAGE_SHIFT; fset = kzalloc(sizeof(*fset), GFP_KERNEL); if (!fset) goto error; -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
