Re: [PATCH v3 1/4] memcg: introduce per-memcg reclaim interface

On Fri, Apr 08, 2022 at 04:57:40AM +0000, Yosry Ahmed wrote:

+static ssize_t memory_reclaim(struct kernfs_open_file *of, char *buf,

• 	      size_t nbytes, loff_t off)
  

+{

• struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
• unsigned int nr_retries = MAX_RECLAIM_RETRIES;
• unsigned long nr_to_reclaim, nr_reclaimed = 0;
• int err;
• buf = strstrip(buf);
• err = page_counter_memparse(buf, "", &nr_to_reclaim);

Is there a reason not to support "max"? Empty string seems odd to me here.

• if (err)

• return err;
  

• while (nr_reclaimed < nr_to_reclaim) {

• unsigned long reclaimed;
  

• if (signal_pending(current))
  

• 	break;
  

I think this should be `return -EINTR;`

• reclaimed = try_to_free_mem_cgroup_pages(memcg,
  

• 				nr_to_reclaim - nr_reclaimed,
  

• 				GFP_KERNEL, true);
  

• if (!reclaimed && !nr_retries--)
  

• 	break;
  

Here you can just `return -EAGAIN;`

• nr_reclaimed += reclaimed;
  

• }
• return nr_reclaimed < nr_to_reclaim ? -EAGAIN : nbytes;

Then this can just be `return nbytes;`

I'm very much in favor of this new interface. Thanks for working on it!