linux-kernel - Re: [PATCH 0/8] tracing: introducing eventfs

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Message-ID: <68D75872-2495-48E6-970F-6A414EEBE3BC@vmware.com>
Date:   Wed, 29 Mar 2023 18:00:22 +0000
From:   Ajay Kaher <akaher@...are.com>
To:     Steven Rostedt <rostedt@...dmis.org>
CC:     "mhiramat@...nel.org" <mhiramat@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-trace-kernel@...r.kernel.org" 
        <linux-trace-kernel@...r.kernel.org>,
        "chinglinyu@...gle.com" <chinglinyu@...gle.com>,
        Nadav Amit <namit@...are.com>,
        Srivatsa Bhat <srivatsab@...are.com>,
        "srivatsa@...il.mit.edu" <srivatsa@...il.mit.edu>,
        Alexey Makhalov <amakhalov@...are.com>,
        Vasavi Sirnapalli <vsirnapalli@...are.com>,
        Tapas Kundu <tkundu@...are.com>,
        "er.ajay.kaher@...il.com" <er.ajay.kaher@...il.com>
Subject: Re: [PATCH 0/8] tracing: introducing eventfs



> On 29-Mar-2023, at 4:17 AM, Steven Rostedt <rostedt@...dmis.org> wrote:
> 
> !! External Email
> 
> On Sun, 22 Jan 2023 22:37:08 +0530
> Ajay Kaher <akaher@...are.com> wrote:
> 
>> Events Tracing infrastructure contains lot of files, directories
>> (internally in terms of inodes, dentries). And ends up by consuming
>> memory in MBs. We can have multiple events of Events Tracing, which
>> further requires more memory.
>> 
>> Instead of creating inodes/dentries, eventfs could keep meta-data and
>> skip the creation of inodes/dentries. As and when require, eventfs will
>> create the inodes/dentries only for required files/directories.
>> Also eventfs would delete the inodes/dentries once no more requires
>> but preserve the meta data.
>> 
> 
> Hi Ajay,
> 
> Is there going to be any more work on this?
> 
> -- Steve

Yes, Steve.

While running tools/testing/selftests/ftrace/ftracetests got crashes, as you also mentioned.
These crashes are because of lack of synchronisation and bugs in eventfs clean up path.

Locally I have fixed all these crashes with the help of Alexey.
I need one internal review round, once done I will post v2.

-Ajay


> 
>> Tracing events took ~9MB, with this approach it took ~4.5MB
>> for ~10K files/dir.
>> 
>> [PATCH 1/8]: Introducing struct tracefs_inode
>> [PATCH 2/8]: Adding eventfs-dir-add functions
>> [PATCH 3/8]: Adding eventfs-file-add function
>> [PATCH 4/8]: Adding eventfs-file-directory-remove function
>> [PATCH 5/8]: Adding functions to create-eventfs-files
>> [PATCH 6/8]: Adding eventfs lookup, read, open functions
>> [PATCH 7/8]: Creating tracefs_inode_cache
>> [PATCH 8/8]: Moving tracing events to eventfs
> 
> 
> !! External Email: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender.