linux-kernel - Re: [PATCH 5/6] dax: add tracepoints to dax_pmd_load

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Message-ID: <20161124092000.GD24138@quack2.suse.cz>
Date:   Thu, 24 Nov 2016 10:20:00 +0100
From:   Jan Kara <jack@...e.cz>
To:     Ross Zwisler <ross.zwisler@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Hellwig <hch@....de>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Chinner <david@...morbit.com>,
        Ingo Molnar <mingo@...hat.com>, Jan Kara <jack@...e.cz>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-nvdimm@...ts.01.org
Subject: Re: [PATCH 5/6] dax: add tracepoints to dax_pmd_load_hole()

On Wed 23-11-16 11:44:21, Ross Zwisler wrote:
> Add tracepoints to dax_pmd_load_hole(), following the same logging
> conventions as the tracepoints in dax_iomap_pmd_fault().
> 
> Here is an example PMD fault showing the new tracepoints:
> 
> read_big-1393  [007] ....    32.133809: dax_pmd_fault: shared mapping read
> address 0x10400000 vm_start 0x10200000 vm_end 0x10600000 pgoff 0x200
> max_pgoff 0x1400
> 
> read_big-1393  [007] ....    32.134067: dax_pmd_load_hole: shared mapping
> read address 0x10400000 zero_page ffffea0002b98000 radix_entry 0x1e
> 
> read_big-1393  [007] ....    32.134069: dax_pmd_fault_done: shared mapping
> read address 0x10400000 vm_start 0x10200000 vm_end 0x10600000 pgoff 0x200
> max_pgoff 0x1400 NOPAGE
> 
> Signed-off-by: Ross Zwisler <ross.zwisler@...ux.intel.com>

Looks good. You can add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza
> ---
>  fs/dax.c                      | 13 +++++++++----
>  include/trace/events/fs_dax.h | 32 ++++++++++++++++++++++++++++++++
>  2 files changed, 41 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/dax.c b/fs/dax.c
> index 1aa7616..2824414 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -1269,32 +1269,37 @@ static int dax_pmd_load_hole(struct vm_area_struct *vma, pmd_t *pmd,
>  	struct address_space *mapping = vma->vm_file->f_mapping;
>  	unsigned long pmd_addr = address & PMD_MASK;
>  	struct page *zero_page;
> +	void *ret = NULL;
>  	spinlock_t *ptl;
>  	pmd_t pmd_entry;
> -	void *ret;
>  
>  	zero_page = mm_get_huge_zero_page(vma->vm_mm);
>  
>  	if (unlikely(!zero_page))
> -		return VM_FAULT_FALLBACK;
> +		goto fallback;
>  
>  	ret = dax_insert_mapping_entry(mapping, vmf, *entryp, 0,
>  			RADIX_DAX_PMD | RADIX_DAX_HZP);
>  	if (IS_ERR(ret))
> -		return VM_FAULT_FALLBACK;
> +		goto fallback;
>  	*entryp = ret;
>  
>  	ptl = pmd_lock(vma->vm_mm, pmd);
>  	if (!pmd_none(*pmd)) {
>  		spin_unlock(ptl);
> -		return VM_FAULT_FALLBACK;
> +		goto fallback;
>  	}
>  
>  	pmd_entry = mk_pmd(zero_page, vma->vm_page_prot);
>  	pmd_entry = pmd_mkhuge(pmd_entry);
>  	set_pmd_at(vma->vm_mm, pmd_addr, pmd, pmd_entry);
>  	spin_unlock(ptl);
> +	trace_dax_pmd_load_hole(vma, address, zero_page, ret);
>  	return VM_FAULT_NOPAGE;
> +
> +fallback:
> +	trace_dax_pmd_load_hole_fallback(vma, address, zero_page, ret);
> +	return VM_FAULT_FALLBACK;
>  }
>  
>  int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
> diff --git a/include/trace/events/fs_dax.h b/include/trace/events/fs_dax.h
> index f9ed4eb..8814b1a 100644
> --- a/include/trace/events/fs_dax.h
> +++ b/include/trace/events/fs_dax.h
> @@ -54,6 +54,38 @@ DEFINE_EVENT(dax_pmd_fault_class, name, \
>  DEFINE_PMD_FAULT_EVENT(dax_pmd_fault);
>  DEFINE_PMD_FAULT_EVENT(dax_pmd_fault_done);
>  
> +DECLARE_EVENT_CLASS(dax_pmd_load_hole_class,
> +	TP_PROTO(struct vm_area_struct *vma, unsigned long address,
> +		struct page *zero_page, void *radix_entry),
> +	TP_ARGS(vma, address, zero_page, radix_entry),
> +	TP_STRUCT__entry(
> +		__field(unsigned long, vm_flags)
> +		__field(unsigned long, address)
> +		__field(struct page *, zero_page)
> +		__field(void *, radix_entry)
> +	),
> +	TP_fast_assign(
> +		__entry->vm_flags = vma->vm_flags;
> +		__entry->address = address;
> +		__entry->zero_page = zero_page;
> +		__entry->radix_entry = radix_entry;
> +	),
> +	TP_printk("%s mapping read address %#lx zero_page %p radix_entry %#lx",
> +		__entry->vm_flags & VM_SHARED ? "shared" : "private",
> +		__entry->address,
> +		__entry->zero_page,
> +		(unsigned long)__entry->radix_entry
> +	)
> +)
> +
> +#define DEFINE_PMD_LOAD_HOLE_EVENT(name) \
> +DEFINE_EVENT(dax_pmd_load_hole_class, name, \
> +	TP_PROTO(struct vm_area_struct *vma, unsigned long address, \
> +		struct page *zero_page, void *radix_entry), \
> +	TP_ARGS(vma, address, zero_page, radix_entry))
> +
> +DEFINE_PMD_LOAD_HOLE_EVENT(dax_pmd_load_hole);
> +DEFINE_PMD_LOAD_HOLE_EVENT(dax_pmd_load_hole_fallback);
>  
>  #endif /* _TRACE_FS_DAX_H */
>  
> -- 
> 2.7.4
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR