[Lustre-devel] [PATCH] Fix task IO accounting on reads

Mark Hills Mark.Hills at framestore.com
Wed Apr 27 04:23:57 PDT 2011


On Tue, 26 Apr 2011, Andreas Dilger wrote:

> On 2011-04-26, at 10:06 AM, Mark Hills wrote:
> > We've often found it inconvenient that reads from Lustre mounts do not 
> > correctly increment IO counts (/proc/<pid>/io).
> > 
> > Below is a patch which aims to fix this functionality.
> > 
> > The symptom is that writes are accounted for, but not reads. It seems that 
> > the accounting it normally done in the kernels page writeback and 
> > readahead functionality. Therefore as Lustre implements its own readahead, 
> > it must also maintain its own accounting on reads (but not writes).
> > 
> > Is anyone able to confirm this rationale for the location of this 
> > particular call, and consider the following patch? Thanks.
> 
> Mark,
> It looks like this functionality was added to the kernel in Git commit 
> hash 7c3ab7381e79dfc7db14a67c6f4f3285664e1ec2, which was between 2.6.19 
> and 2.6.20.  This call needs to be made conditional so that it doesn't 
> break the client build on older kernels (it looks like it would break 
> RHEL5 and SLES10 clients, which don't have this functionality AFAICS).
> 
> It looks like it may be possible to create a compatibility macro in 
> lustre/include/linux/lustre_compat25.h so that it doesn't break for 
> clients running on older kernels:
> 
> #ifdef CONFIG_TASK_IO_ACCOUNTING
> #include <linux/task_io_accounting_ops.h>
> #else
> #define task_io_accounting_read(bytes) do {} while (0)
> #endif

Newer kernels always define task_io_account_read() as a function, even if 
it's a no-op. So to avoid redefining it it should check the kernel 
version, not the CONFIG_ flag.

A revised patch is below, which I tested with kernel 2.6.32.28. 
Unfortunately I odn't have a pre-2.6.20 platform for testing.

Thanks Andreas,

-- 
Mark

---
 lustre/include/linux/lustre_compat25.h |    6 ++++++
 lustre/llite/rw.c                      |    2 ++
 2 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/lustre/include/linux/lustre_compat25.h b/lustre/include/linux/lustre_compat25.h
index 81865d0..666374b 100644
--- a/lustre/include/linux/lustre_compat25.h
+++ b/lustre/include/linux/lustre_compat25.h
@@ -143,6 +143,12 @@ void groups_free(struct group_info *ginfo);
 
 #endif /* LINUX_VERSION_CODE < KERNEL_VERSION(2,6,4) */
 
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,20)
+#define task_io_account_read(bytes) do {} while (0)
+#else
+#include <linux/task_io_accounting_ops.h>
+#endif
+
 #ifndef page_private
 #define page_private(page) ((page)->private)
 #define set_page_private(page, v) ((page)->private = (v))
diff --git a/lustre/llite/rw.c b/lustre/llite/rw.c
index ccd6a42..1fddd5b 100644
--- a/lustre/llite/rw.c
+++ b/lustre/llite/rw.c
@@ -1311,6 +1311,8 @@ static int ll_issue_page_read(struct obd_export *exp,
         if (rc) {
                 LL_CDEBUG_PAGE(D_ERROR, page, "read queue failed: rc %d\n", rc);
                 page_cache_release(page);
+        } else {
+                task_io_account_read(CFS_PAGE_SIZE);
         }
         RETURN(rc);
 }
-- 
1.7.1.1




More information about the lustre-devel mailing list