[PATCH 1/2] util/bufferiszero: assign length_to_accel value for each accelerator case

[PATCH 1/2] util/bufferiszero: assign length_to_accel value for each accelerator case

[Robert Hoo]

Because in unit test, init_accel() will be called several times, each with
different accelerator type.

Signed-off-by: Robert Hoo <robert.hu@linux.intel.com>
---
 util/bufferiszero.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/util/bufferiszero.c b/util/bufferiszero.c
index 6639035..b801253 100644
--- a/util/bufferiszero.c
+++ b/util/bufferiszero.c
@@ -254,13 +254,16 @@ static void init_accel(unsigned cache)
     bool (*fn)(const void *, size_t) = buffer_zero_int;
     if (cache & CACHE_SSE2) {
         fn = buffer_zero_sse2;
+        length_to_accel = 64;
     }
 #ifdef CONFIG_AVX2_OPT
     if (cache & CACHE_SSE4) {
         fn = buffer_zero_sse4;
+        length_to_accel = 64;
     }
     if (cache & CACHE_AVX2) {
         fn = buffer_zero_avx2;
+        length_to_accel = 64;
     }
 #endif
 #ifdef CONFIG_AVX512F_OPT
-- 
1.8.3.1

[PATCH 2/2] util/bufferiszero: improve avx2 accelerator

[Robert Hoo]

By increasing avx2 length_to_accel to 128, we can simplify its logic and reduce a
branch.

The authorship of this patch actually belongs to Richard Henderson <richard.henderson@linaro.org>,
I just fix a boudary case on his original patch.

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Robert Hoo <robert.hu@linux.intel.com>
---
 util/bufferiszero.c | 26 +++++++++-----------------
 1 file changed, 9 insertions(+), 17 deletions(-)

diff --git a/util/bufferiszero.c b/util/bufferiszero.c
index b801253..695bb4c 100644
--- a/util/bufferiszero.c
+++ b/util/bufferiszero.c
@@ -158,27 +158,19 @@ buffer_zero_avx2(const void *buf, size_t len)
     __m256i *p = (__m256i *)(((uintptr_t)buf + 5 * 32) & -32);
     __m256i *e = (__m256i *)(((uintptr_t)buf + len) & -32);
 
-    if (likely(p <= e)) {
-        /* Loop over 32-byte aligned blocks of 128.  */
-        do {
-            __builtin_prefetch(p);
-            if (unlikely(!_mm256_testz_si256(t, t))) {
-                return false;
-            }
-            t = p[-4] | p[-3] | p[-2] | p[-1];
-            p += 4;
-        } while (p <= e);
-    } else {
-        t |= _mm256_loadu_si256(buf + 32);
-        if (len <= 128) {
-            goto last2;
+    /* Loop over 32-byte aligned blocks of 128.  */
+    while (p <= e) {
+        __builtin_prefetch(p);
+        if (unlikely(!_mm256_testz_si256(t, t))) {
+            return false;
         }
-    }
+        t = p[-4] | p[-3] | p[-2] | p[-1];
+        p += 4;
+    } ;
 
     /* Finish the last block of 128 unaligned.  */
     t |= _mm256_loadu_si256(buf + len - 4 * 32);
     t |= _mm256_loadu_si256(buf + len - 3 * 32);
- last2:
     t |= _mm256_loadu_si256(buf + len - 2 * 32);
     t |= _mm256_loadu_si256(buf + len - 1 * 32);
 
@@ -263,7 +255,7 @@ static void init_accel(unsigned cache)
     }
     if (cache & CACHE_AVX2) {
         fn = buffer_zero_avx2;
-        length_to_accel = 64;
+        length_to_accel = 128;
     }
 #endif
 #ifdef CONFIG_AVX512F_OPT
-- 
1.8.3.1

Re: [PATCH 2/2] util/bufferiszero: improve avx2 accelerator

[Eric Blake]

On 3/25/20 1:50 AM, Robert Hoo wrote:
> By increasing avx2 length_to_accel to 128, we can simplify its logic and reduce a
> branch.
> 
> The authorship of this patch actually belongs to Richard Henderson <richard.henderson@linaro.org>,

Long line; it's nice to wrap commit messages around column 70 or so 
(because reading 'git log' in an 80-column window adds indentation).

> I just fix a boudary case on his original patch.

boundary

> 
> Suggested-by: Richard Henderson <richard.henderson@linaro.org>
> Signed-off-by: Robert Hoo <robert.hu@linux.intel.com>
> ---
>   util/bufferiszero.c | 26 +++++++++-----------------
>   1 file changed, 9 insertions(+), 17 deletions(-)
> 


-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

RE: [PATCH 2/2] util/bufferiszero: improve avx2 accelerator

[Hu, Robert]

(Don't know why my Linux-Evolution missed this mail.)
> -----Original Message-----
> From: Eric Blake <eblake@redhat.com>
> Sent: Wednesday, March 25, 2020 20:54
> To: Robert Hoo <robert.hu@linux.intel.com>; qemu-devel@nongnu.org;
> pbonzini@redhat.com; richard.henderson@linaro.org
> Cc: Hu, Robert <robert.hu@intel.com>
> Subject: Re: [PATCH 2/2] util/bufferiszero: improve avx2 accelerator
> 
> On 3/25/20 1:50 AM, Robert Hoo wrote:
> > By increasing avx2 length_to_accel to 128, we can simplify its logic
> > and reduce a branch.
> >
> > The authorship of this patch actually belongs to Richard Henderson
> > <richard.henderson@linaro.org>,
> 
> Long line; it's nice to wrap commit messages around column 70 or so (because
> reading 'git log' in an 80-column window adds indentation).
> 
[Hu, Robert] 
I think I set my vim on wrap. This probably escaped by paste.
I ran checkpatch.pl on the patches before sending. It escaped check but didn't
escaped your eagle eye😊 Thank you.

> > I just fix a boudary case on his original patch.
> 
> boundary
[Hu, Robert] 
Emm... again spell error. Usually I would paste descriptions into some editors
with spell check, but forgot this time.
Vim doesn't have spell check I think. What editor would you suggest me to
integrate with git editing?

BTW, do I need to resend these 2 patches?
> 
> >
> > Suggested-by: Richard Henderson <richard.henderson@linaro.org>
> > Signed-off-by: Robert Hoo <robert.hu@linux.intel.com>
> > ---
> >   util/bufferiszero.c | 26 +++++++++-----------------
> >   1 file changed, 9 insertions(+), 17 deletions(-)
> >
> 
> 
> --
> Eric Blake, Principal Software Engineer
> Red Hat, Inc.           +1-919-301-3226
> Virtualization:  qemu.org | libvirt.org

Re: [PATCH 2/2] util/bufferiszero: improve avx2 accelerator

[Paolo Bonzini]

On 26/03/20 03:09, Hu, Robert wrote:
> BTW, do I need to resend these 2 patches?

No, thanks!  I have queued them.

Paolo

Re: [PATCH 2/2] util/bufferiszero: improve avx2 accelerator

[Eric Blake]

On 3/25/20 9:09 PM, Hu, Robert wrote:
> (Don't know why my Linux-Evolution missed this mail.)
>> -----Original Message-----

>> Long line; it's nice to wrap commit messages around column 70 or so (because
>> reading 'git log' in an 80-column window adds indentation).
>>
> [Hu, Robert]
> I think I set my vim on wrap. This probably escaped by paste.
> I ran checkpatch.pl on the patches before sending. It escaped check but didn't
> escaped your eagle eye😊 Thank you.

checkpatch doesn't flag commit message long lines.  Maybe it could be 
patched to do so, but it's not at the top of my list to write that patch.

> 
>>> I just fix a boudary case on his original patch.
>>
>> boundary
> [Hu, Robert]
> Emm... again spell error. Usually I would paste descriptions into some editors
> with spell check, but forgot this time.
> Vim doesn't have spell check I think. What editor would you suggest me to
> integrate with git editing?

I'm an emacs user, so I have no suggestions for vim, but I'd be very 
surprised if there were not some vim expert online that could figure out 
how to wire in a spell-checker to vim.  Google quickly finds: 
https://www.ostechnix.com/use-spell-check-feature-vim-text-editor/

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

Re: [PATCH 2/2] util/bufferiszero: improve avx2 accelerator

[Robert Hoo]

On Thu, 2020-03-26 at 08:26 -0500, Eric Blake wrote:
> On 3/25/20 9:09 PM, Hu, Robert wrote:
> > (Don't know why my Linux-Evolution missed this mail.)
> > > -----Original Message-----
> > > Long line; it's nice to wrap commit messages around column 70 or
> > > so (because
> > > reading 'git log' in an 80-column window adds indentation).
> > > 
> > 
> > [Hu, Robert]
> > I think I set my vim on wrap. This probably escaped by paste.
> > I ran checkpatch.pl on the patches before sending. It escaped check
> > but didn't
> > escaped your eagle eye😊 Thank you.
> 
> checkpatch doesn't flag commit message long lines.  Maybe it could
> be 
> patched to do so, but it's not at the top of my list to write that
> patch.
> 
> > 
> > > > I just fix a boudary case on his original patch.
> > > 
> > > boundary
> > 
> > [Hu, Robert]
> > Emm... again spell error. Usually I would paste descriptions into
> > some editors
> > with spell check, but forgot this time.
> > Vim doesn't have spell check I think. What editor would you suggest
> > me to
> > integrate with git editing?
> 
> I'm an emacs user, so I have no suggestions for vim, but I'd be very 
> surprised if there were not some vim expert online that could figure
> out 
> how to wire in a spell-checker to vim.  Google quickly finds: 
> https://www.ostechnix.com/use-spell-check-feature-vim-text-editor/
> 
nice, thanks:)