Re: [PATCH] VM: kswapd should not do blocking memory allocations

Wu Fengguang
2010-08-20T05:45:40Z

> Hi Ram,
>
> I was seeing it on NFS until I put in the following kswapd-specific hack
> into nfs_release_page():
>
> /* Only do I/O if gfp is a superset of GFP_KERNEL */
> if (mapping && (gfp & GFP_KERNEL) == GFP_KERNEL) {
> int how = FLUSH_SYNC;
>
> /* Don't let kswapd deadlock waiting for OOM RPC calls */
> if (current_is_kswapd())
> how = 0;

So the patch can remove the above workaround together, and add comment
that NFS exploits the gfp mask to avoid complex operations involving
recursive memory allocation and hence deadlock?

Thanks,
Fengguang

> nfs_commit_inode(mapping->host, how);
> }
>
> Remove the 'if (current_is_kswapd())' line, and run an mmap() write
> intensive workload, and it should hang pretty much every time.
>
> Cheers
> Trond
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/