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* [PATCH] uevent_can_discard: optimize devpath check
@ 2017-03-01 17:22 Martin Wilck
  2017-03-16  6:42 ` Christophe Varoqui
  0 siblings, 1 reply; 3+ messages in thread
From: Martin Wilck @ 2017-03-01 17:22 UTC (permalink / raw)
  To: tang.junhui, dm-devel

This uses roughly 10% cycles of the sscanf-based implementation.

Improves: ee8888f0 "multipath-tools: improve processing efficiency..."
Signed-off-by: Martin Wilck <mwilck@suse.com>
---
 libmultipath/uevent.c | 37 +++++++++++++++++++++++--------------
 1 file changed, 23 insertions(+), 14 deletions(-)

diff --git a/libmultipath/uevent.c b/libmultipath/uevent.c
index 6e2527bd..367e129a 100644
--- a/libmultipath/uevent.c
+++ b/libmultipath/uevent.c
@@ -143,26 +143,35 @@ uevent_need_merge(void)
 	return need_merge;
 }
 
+static bool
+uevent_can_discard_by_devpath(const char *devpath)
+{
+	static const char BLOCK[] = "/block/";
+	const char *tmp = strstr(devpath, BLOCK);
+
+	if (tmp == NULL) {
+		condlog(4, "no /block/ in '%s'", devpath);
+		return true;
+	}
+	tmp += sizeof(BLOCK) - 1;
+	if (*tmp == '\0')
+		/* just ".../block/" - discard */
+		return true;
+	/*
+	 * If there are more path elements after ".../block/xyz",
+	 * it's a partition - discard it; but don't discard ".../block/sda/".
+	 */
+	tmp = strchr(tmp, '/');
+	return tmp != NULL && *(tmp + 1) != '\0';
+}
+
 bool
 uevent_can_discard(struct uevent *uev)
 {
-	char *tmp;
-	char a[11], b[11];
 	struct config * conf;
 
-	/*
-	 * keep only block devices, discard partitions
-	 */
-	tmp = strstr(uev->devpath, "/block/");
-	if (tmp == NULL){
-		condlog(4, "no /block/ in '%s'", uev->devpath);
+	if (uevent_can_discard_by_devpath(uev->devpath))
 		return true;
-	}
-	if (sscanf(tmp, "/block/%10s", a) != 1 ||
-	    sscanf(tmp, "/block/%10[^/]/%10s", a, b) == 2) {
-		condlog(4, "discard event on %s", uev->devpath);
-		return true;
-	}
 
 	/* 
 	 * do not filter dm devices by devnode
-- 
2.12.0

^ permalink raw reply related	[flat|nested] 3+ messages in thread
* Re: [PATCH] uevent_can_discard: optimize devpath check
  2017-03-01 17:22 [PATCH] uevent_can_discard: optimize devpath check Martin Wilck
@ 2017-03-16  6:42 ` Christophe Varoqui
  0 siblings, 0 replies; 3+ messages in thread
From: Christophe Varoqui @ 2017-03-16  6:42 UTC (permalink / raw)
  To: Martin Wilck; +Cc: device-mapper development, tang.junhui


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Applied.
Thanks.

On Wed, Mar 1, 2017 at 6:22 PM, Martin Wilck <mwilck@suse.com> wrote:

> This uses roughly 10% cycles of the sscanf-based implementation.
>
> Improves: ee8888f0 "multipath-tools: improve processing efficiency..."
> Signed-off-by: Martin Wilck <mwilck@suse.com>
> ---
>  libmultipath/uevent.c | 37 +++++++++++++++++++++++--------------
>  1 file changed, 23 insertions(+), 14 deletions(-)
>
> diff --git a/libmultipath/uevent.c b/libmultipath/uevent.c
> index 6e2527bd..367e129a 100644
> --- a/libmultipath/uevent.c
> +++ b/libmultipath/uevent.c
> @@ -143,26 +143,35 @@ uevent_need_merge(void)
>         return need_merge;
>  }
>
> +static bool
> +uevent_can_discard_by_devpath(const char *devpath)
> +{
> +       static const char BLOCK[] = "/block/";
> +       const char *tmp = strstr(devpath, BLOCK);
> +
> +       if (tmp == NULL) {
> +               condlog(4, "no /block/ in '%s'", devpath);
> +               return true;
> +       }
> +       tmp += sizeof(BLOCK) - 1;
> +       if (*tmp == '\0')
> +               /* just ".../block/" - discard */
> +               return true;
> +       /*
> +        * If there are more path elements after ".../block/xyz",
> +        * it's a partition - discard it; but don't discard
> ".../block/sda/".
> +        */
> +       tmp = strchr(tmp, '/');
> +       return tmp != NULL && *(tmp + 1) != '\0';
> +}
> +
>  bool
>  uevent_can_discard(struct uevent *uev)
>  {
> -       char *tmp;
> -       char a[11], b[11];
>         struct config * conf;
>
> -       /*
> -        * keep only block devices, discard partitions
> -        */
> -       tmp = strstr(uev->devpath, "/block/");
> -       if (tmp == NULL){
> -               condlog(4, "no /block/ in '%s'", uev->devpath);
> +       if (uevent_can_discard_by_devpath(uev->devpath))
>                 return true;
> -       }
> -       if (sscanf(tmp, "/block/%10s", a) != 1 ||
> -           sscanf(tmp, "/block/%10[^/]/%10s", a, b) == 2) {
> -               condlog(4, "discard event on %s", uev->devpath);
> -               return true;
> -       }
>
>         /*
>          * do not filter dm devices by devnode
> --
> 2.12.0
>
> --
> dm-devel mailing list
> dm-devel@redhat.com
> https://www.redhat.com/mailman/listinfo/dm-devel
>

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^ permalink raw reply	[flat|nested] 3+ messages in thread
* Re: [PATCH] uevent_can_discard: optimize devpath check
@ 2017-03-02  8:35 tang.junhui
  0 siblings, 0 replies; 3+ messages in thread
From: tang.junhui @ 2017-03-02  8:35 UTC (permalink / raw)
  To: mwilck; +Cc: dm-devel


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It  looks fine to me.




Regards,

Tang Junhui




＞ This uses roughly 10% cycles of the sscanf-based implementation.

＞ 

＞ Improves: ee8888f0 "multipath-tools: improve processing efficiency..."

＞ Signed-off-by: Martin Wilck ＜mwilck@suse.com＞

＞ ---

＞  libmultipath/uevent.c | 37 +++++++++++++++++++++++--------------

＞  1 file changed, 23 insertions(+), 14 deletions(-)

＞ 

＞ diff --git a/libmultipath/uevent.c b/libmultipath/uevent.c

＞ index 6e2527bd..367e129a 100644

＞ --- a/libmultipath/uevent.c

＞ +++ b/libmultipath/uevent.c

＞ @@ -143,26 +143,35 @@ uevent_need_merge(void)

＞      return need_merge

＞  }

＞  

＞ +static bool

＞ +uevent_can_discard_by_devpath(const char *devpath)

＞ +{

＞ +    static const char BLOCK[] = "/block/"

＞ +    const char *tmp = strstr(devpath, BLOCK)

＞ +

＞ +    if (tmp == NULL) {

＞ +        condlog(4, "no /block/ in '%s'", devpath)

＞ +        return true

＞ +    }

＞ +    tmp += sizeof(BLOCK) - 1

＞ +    if (*tmp == '\0')

＞ +        /* just ".../block/" - discard */

＞ +        return true

＞ +    /*

＞ +     * If there are more path elements after ".../block/xyz",

＞ +     * it's a partition - discard it but don't discard ".../block/sda/".

＞ +     */

＞ +    tmp = strchr(tmp, '/')

＞ +    return tmp != NULL && *(tmp + 1) != '\0'

＞ +}

＞ +

＞  bool

＞  uevent_can_discard(struct uevent *uev)

＞  {

＞ -    char *tmp

＞ -    char a[11], b[11]

＞      struct config * conf

＞  

＞ -    /*

＞ -     * keep only block devices, discard partitions

＞ -     */

＞ -    tmp = strstr(uev-＞devpath, "/block/")

＞ -    if (tmp == NULL){

＞ -        condlog(4, "no /block/ in '%s'", uev-＞devpath)

＞ +    if (uevent_can_discard_by_devpath(uev-＞devpath))

＞          return true

＞ -    }

＞ -    if (sscanf(tmp, "/block/%10s", a) != 1 ||

＞ -        sscanf(tmp, "/block/%10[^/]/%10s", a, b) == 2) {

＞ -        condlog(4, "discard event on %s", uev-＞devpath)

＞ -        return true

＞ -    }

＞  

＞      /* 

＞       * do not filter dm devices by devnode

＞ -- 

＞ 2.12.0

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^ permalink raw reply	[flat|nested] 3+ messages in thread
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2017-03-01 17:22 [PATCH] uevent_can_discard: optimize devpath check Martin Wilck
2017-03-16  6:42 ` Christophe Varoqui
2017-03-02  8:35 tang.junhui

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