From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Nelson <eric@nelint.com>
Date: Mon, 21 Mar 2016 07:27:34 -0700
Subject: [U-Boot] [RFC PATCH 2/2] mmc: add support for block device cache
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Hi Stephen,

On 03/20/2016 12:35 PM, Eric Nelson wrote:
> On 03/17/2016 02:23 PM, Stephen Warren wrote:
>> On 03/16/2016 03:40 PM, Eric Nelson wrote:
...
>> Do you have any stats on how many operations this saves for typical FS
>> operations such as:
>>
>> - Partition table type identification (with various types such as
>> MBR/DOS, GPT, ...)
>> - Partition enumeration
>> - Filesystem identification (with various filesystems such as FAT, ext,
>> ...)
>> - File reads
>>
> 
> Not yet, but I'm working something up that will allow this to be
> gathered easily. As soon as we implement a cache, it provides a nice
> spot for tracing operations.
> 

The V2 RFC patch set implements a command (blkcache) that allows
tracing block read operations as they pass through the cache, among
other things:

=> blkcache trace
=> load mmc 0 10008000 /zImage
miss: start 0, count 1
fill: start 0, count 1
miss: start 2000, count 1
fill: start 2000, count 1
reading /zImage
hit: start 2000, count 1
miss: start 2011, count 2
miss: start 2001, count 6
miss: start 2031, count 9678
miss: start 45ff, count 1
fill: start 45ff, count 1
4955304 bytes read in 258 ms (18.3 MiB/s)

http://lists.denx.de/pipermail/u-boot/2016-March/249155.html
https://patchwork.ozlabs.org/patch/599942/