linux-kernel - Re: [PATCH] init : Reduce rootwait polling interval time to 5ms

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Message-Id: <20161207124747.62043547ff990002b8e9b4ee@linux-foundation.org>
Date:   Wed, 7 Dec 2016 12:47:47 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Jungseung Lee <js07.lee@...sung.com>
Cc:     Pierre Ossman <drzeus-list@...eus.cx>,
        Al Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@....de>, Adrian Bunk <bunk@...sta.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] init : Reduce rootwait polling interval time to 5ms

On Wed, 07 Dec 2016 15:07:43 +0900 Jungseung Lee <js07.lee@...sung.com> wrote:

> For several devices, the rootwait time is sensitive because it directly
> affects booting time.
> The polling interval of rootwait is currently 100ms.
> To save unnessesary waiting time, reduce the polling interval to 5 ms.
> 
> ...
>
> --- a/init/do_mounts.c
> +++ b/init/do_mounts.c
> @@ -543,6 +543,8 @@ void __init mount_root(void)
>  #endif
>  }
>  
> +#define ROOTWAIT_MSEC 5
> +
>  /*
>   * Prepare the namespace - decide what/where to mount, load ramdisks, etc.
>   */
> @@ -588,7 +590,7 @@ void __init prepare_namespace(void)
>  			saved_root_name);
>  		while (driver_probe_done() != 0 ||
>  			(ROOT_DEV = name_to_dev_t(saved_root_name)) == 0)
> -			msleep(100);
> +			msleep(ROOTWAIT_MSEC);
>  		async_synchronize_full();
>  	}

Fair enough.  But I don't think the used-once #define adds any value,
so let's go with the simple version?

--- a/init/do_mounts.c~init-reduce-rootwait-polling-interval-time-to-5ms-fix
+++ a/init/do_mounts.c
@@ -543,8 +543,6 @@ void __init mount_root(void)
 #endif
 }
 
-#define ROOTWAIT_MSEC 5
-
 /*
  * Prepare the namespace - decide what/where to mount, load ramdisks, etc.
  */
@@ -590,7 +588,7 @@ void __init prepare_namespace(void)
 			saved_root_name);
 		while (driver_probe_done() != 0 ||
 			(ROOT_DEV = name_to_dev_t(saved_root_name)) == 0)
-			msleep(ROOTWAIT_MSEC);
+			msleep(5);
 		async_synchronize_full();
 	}
 
_