On Thu, Oct 7, 2021 at 11:01 AM Chuck Lever III <chuck.lever@xxxxxxxxxx> wrote:
>
>
>
> > On Oct 7, 2021, at 9:05 AM, David Wysochanski <dwysocha@xxxxxxxxxx> wrote:
> >
> > On Tue, Oct 5, 2021 at 1:14 PM Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
> > >
> > > There are two new events that report slightly different information
> > > for readpage and readpages.
> > >
> > > For readpage:
> > > fsx-1387 [006] 380.761896: nfs_aops_readpage: fileid=00:28:2 fhandle=0x36fbbe51 version=1752899355910932437 page_index=32
> > >
> > > The index of a synchronous single-page read is reported.
> > >
> > > For readpages:
> > >
> > > fsx-1387 [006] 380.760847: nfs_aops_readpages: fileid=00:28:2 fhandle=0x36fbbe51 version=1752899355909932456 nr_pages=3
> > >
> > > The count of pages requested is reported. readpages does not wait
> > > for the READ requests to complete.
> > >
> > > Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> > > ---
> > > fs/nfs/nfstrace.h | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> > > fs/nfs/read.c | 8 ++----
> > > 2 files changed, 72 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/fs/nfs/nfstrace.h b/fs/nfs/nfstrace.h
> > > index e9be65b52bfe..0534d090ee55 100644
> > > --- a/fs/nfs/nfstrace.h
> > > +++ b/fs/nfs/nfstrace.h
> > > @@ -862,6 +862,76 @@ TRACE_EVENT(nfs_sillyrename_unlink,
> > > )
> > > );
> > >
> > > +TRACE_EVENT(nfs_aops_readpage,
> > > + TP_PROTO(
> > > + const struct inode *inode,
> > > + struct page *page
> > > + ),
> > > +
> > > + TP_ARGS(inode, page),
> > > +
> > > + TP_STRUCT__entry(
> > > + __field(dev_t, dev)
> > > + __field(u32, fhandle)
> > > + __field(u64, fileid)
> > > + __field(u64, version)
> > > + __field(pgoff_t, index)
> > > + ),
> > > +
> > > + TP_fast_assign(
> > > + const struct nfs_inode *nfsi = NFS_I(inode);
> > > +
> > > + __entry->dev = inode->i_sb->s_dev;
> > > + __entry->fileid = nfsi->fileid;
> > > + __entry->fhandle = nfs_fhandle_hash(&nfsi->fh);
> > > + __entry->version = inode_peek_iversion_raw(inode);
> > > + __entry->index = page_index(page);
> > > + ),
> > > +
> > > + TP_printk(
> > > + "fileid=%02x:%02x:%llu fhandle=0x%08x version=%llu page_index=%lu",
> > > + MAJOR(__entry->dev), MINOR(__entry->dev),
> > > + (unsigned long long)__entry->fileid,
> > > + __entry->fhandle, __entry->version,
> > > + __entry->index
> > > + )
> > > +);
> > > +
> > > +TRACE_EVENT(nfs_aops_readpages,
> > > + TP_PROTO(
> > > + const struct inode *inode,
> > > + unsigned int nr_pages
> > > + ),
> > > +
> > > + TP_ARGS(inode, nr_pages),
> > > +
> > > + TP_STRUCT__entry(
> > > + __field(dev_t, dev)
> > > + __field(u32, fhandle)
> > > + __field(u64, fileid)
> > > + __field(u64, version)
> > > + __field(unsigned int, nr_pages)
> > > + ),
> > > +
> > > + TP_fast_assign(
> > > + const struct nfs_inode *nfsi = NFS_I(inode);
> > > +
> > > + __entry->dev = inode->i_sb->s_dev;
> > > + __entry->fileid = nfsi->fileid;
> > > + __entry->fhandle = nfs_fhandle_hash(&nfsi->fh);
> > > + __entry->version = inode_peek_iversion_raw(inode);
> > > + __entry->nr_pages = nr_pages;
> > > + ),
> > > +
> > > + TP_printk(
> > > + "fileid=%02x:%02x:%llu fhandle=0x%08x version=%llu nr_pages=%u",
> > > + MAJOR(__entry->dev), MINOR(__entry->dev),
> > > + (unsigned long long)__entry->fileid,
> > > + __entry->fhandle, __entry->version,
> > > + __entry->nr_pages
> > > + )
> > > +);
> > > +
> > > TRACE_EVENT(nfs_initiate_read,
> > > TP_PROTO(
> > > const struct nfs_pgio_header *hdr
> > > diff --git a/fs/nfs/read.c b/fs/nfs/read.c
> > > index 08d6cc57cbc3..94690eda2a88 100644
> > > --- a/fs/nfs/read.c
> > > +++ b/fs/nfs/read.c
> > > @@ -337,8 +337,7 @@ int nfs_readpage(struct file *file, struct page *page)
> > > struct inode *inode = page_file_mapping(page)->host;
> > > int ret;
> > >
> > > - dprintk("NFS: nfs_readpage (%p %ld@%lu)\n",
> > > - page, PAGE_SIZE, page_index(page));
> > > + trace_nfs_aops_readpage(inode, page);
> > > nfs_inc_stats(inode, NFSIOS_VFSREADPAGE);
> > >
> > > /*
> > > @@ -403,10 +402,7 @@ int nfs_readpages(struct file *file, struct address_space *mapping,
> > > struct inode *inode = mapping->host;
> > > int ret;
> > >
> > > - dprintk("NFS: nfs_readpages (%s/%Lu %d)\n",
> > > - inode->i_sb->s_id,
> > > - (unsigned long long)NFS_FILEID(inode),
> > > - nr_pages);
> > > + trace_nfs_aops_readpages(inode, nr_pages);
> > > nfs_inc_stats(inode, NFSIOS_VFSREADPAGES);
> > >
> > > ret = -ESTALE;
> > >
> > >
> >
> > I added this on top of my fscache patches and have been testing.
> > Should we be tracing (only?) the return point with the return
> > value?
>
> The purpose of the entry point is: you get a timestamp, filehandle
> information, and you know what is driving the READ request (sync
> read or async readahead).
>
> There is a dprintk() at the top of the function as well as a
> performance metric counter, but there currently isn't a dprintk()
> at the bottom of the function. So I assumed the return code is
> not a critical piece of information. I'm willing to be educated,
> though.
>
Well, I was trying to understand the various approaches in nfstrace.h.
There are tracepoints that are paired with entry and exit, but I guess
these have multiple pieces of information that may change from
start to finish. Examples:
nfs_refresh_inode_enter
nfs_refresh_inode_exit
nfs_lookup_revalidate_enter
nfs_lookup_revalidate_exit
> A return point trace event could be generated only when there
> is an unexpected error condition, for example, to reduce trace
> log noise?
>
Ok so you would just add a second tracepoint for non-zero returns?
>
> > bigfile-6279 [004] ..... 11550.387232: nfs_aops_readpages: fileid=00:2f:26127 fhandle=0xb6d0e8f0 version=1633611037513339503 nr_pages=32
> > bigfile-6279 [004] ..... 11550.387236: nfs_fscache_page_event_read: fileid=00:2f:26127 fhandle=0xb6d0e8f0 offset=0 count=4096
> > bigfile-6279 [004] ..... 11550.387237: nfs_fscache_page_event_read_done: fileid=00:2f:26127 fhandle=0xb6d0e8f0 offset=0 count=4096 error=-105
> > bigfile-6279 [004] ..... 11550.387248: nfs_fscache_page_event_read: fileid=00:2f:26127 fhandle=0xb6d0e8f0 offset=4096 count=4096
> > bigfile-6279 [004] ..... 11550.387248: nfs_fscache_page_event_read_done: fileid=00:2f:26127 fhandle=0xb6d0e8f0 offset=4096 count=4096 error=-105
> > bigfile-6279 [004] ..... 11550.387250: nfs_fscache_page_event_read: fileid=00:2f:26127 fhandle=0xb6d0e8f0 offset=8192 count=4096
> > bigfile-6279 [004] ..... 11550.387250: nfs_fscache_page_event_read_done: fileid=00:2f:26127 fhandle=0xb6d0e8f0 offset=8192 count=4096 error=-105
Example:
bigfile-6279 [004] ..... 11550.387252: nfs_aops_readpages_error:
fileid=00:2f:26127 fhandle=0xb6d0e8f0 version=1633611037513339503
nr_pages=6 error=-5
>
> --
> Chuck Lever
>
>
>
