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Date:   Sat, 10 Apr 2021 09:05:32 +0800
From:   Wu Fengguang <wfg@mail.ustc.edu.cn>
To:     Hui Zhu <teawater@gmail.com>
Cc:     linux-kernel@vger.kernel.org
Subject: Re: [PATCH for vm-scalability] usemem: Add code for touch-alloc
Message-ID: <20210410010532.GA339619@wfg-e595>
References: <20210408134255.12330-1-teawater@gmail.com>
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In-Reply-To: <20210408134255.12330-1-teawater@gmail.com>
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Applied, thanks!

On Thu, Apr 08, 2021 at 09:42:55PM +0800, Hui Zhu wrote:
>Add code for touch-alloc.
>And Change read memory to write memory to avoid use the zero-page for
>reads in do_anonymous_page.
>
>Signed-off-by: Hui Zhu <teawater@gmail.com>
>---
> usemem.c | 34 ++++++++++++++++++++++------------
> 1 file changed, 22 insertions(+), 12 deletions(-)
>
>diff --git a/usemem.c b/usemem.c
>index e2c46ec..5b90aae 100644
>--- a/usemem.c
>+++ b/usemem.c
>@@ -329,6 +329,18 @@ void detach(void)
> 	}
> }
>
>+unsigned long do_access(unsigned long *p, unsigned long idx, int read)
>+{
>+	volatile unsigned long *vp = p;
>+
>+	if (read)
>+		return vp[idx];	/* read data */
>+	else {
>+		vp[idx] = idx;	/* write data */
>+		return 0;
>+	}
>+}
>+
> unsigned long * allocate(unsigned long bytes)
> {
> 	unsigned long *p;
>@@ -355,6 +367,14 @@ unsigned long * allocate(unsigned long bytes)
> 		p = (unsigned long *)ALIGN((unsigned long)p, pagesize - 1);
> 	}
>
>+	if (opt_touch_alloc) {
>+		unsigned long i;
>+		unsigned long m = bytes / sizeof(*p);
>+
>+		for (i = 0; i < m; i += 1)
>+			do_access(p, i, 0);
>+	}
>+
> 	return p;
> }
>
>@@ -436,18 +456,6 @@ void shm_unlock(int seg_id)
> 	shmctl(seg_id, SHM_UNLOCK, NULL);
> }
>
>-unsigned long do_access(unsigned long *p, unsigned long idx, int read)
>-{
>-	volatile unsigned long *vp = p;
>-
>-	if (read)
>-		return vp[idx];	/* read data */
>-	else {
>-		vp[idx] = idx;	/* write data */
>-		return 0;
>-	}
>-}
>-
> #define NSEC_PER_SEC  (1UL * 1000 * 1000 * 1000)
>
> long nsec_sub(long nsec1, long nsec2)
>@@ -953,6 +961,8 @@ int main(int argc, char *argv[])
> 				opt_punch_holes = 1;
> 			} else if (strcmp(opts[opt_index].name, "init-time") == 0) {
> 				opt_init_time = 1;
>+			} else if (strcmp(opts[opt_index].name, "touch-alloc") == 0) {
>+				opt_touch_alloc = 1;
> 			} else
> 				usage(1);
> 			break;
>-- 
>2.17.1
>