lkml.org 
[lkml]   [2018]   [May]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] IB/mad: Use ID allocator routines to allocate agent number
    On Tue, May 29, 2018 at 06:16:14PM +0200, Håkon Bugge wrote:
    >
    > > On 29 May 2018, at 17:49, Jason Gunthorpe <jgg@ziepe.ca> wrote:
    > >
    > > On Tue, May 29, 2018 at 09:38:08AM +0200, Hans Westgaard Ry wrote:
    > >> The agent TID is a 64 bit value split in two dwords. The least
    > >> significant dword is the TID running counter. The most significant
    > >> dword is the agent number. In the CX-3 shared port model, the mlx4
    > >> driver uses the most significant byte of the agent number to store the
    > >> slave number, making agent numbers greater and equal to 2^24 (3 bytes)
    > >> unusable.
    > >
    > > There is no reason for this to be an ida, just do something like
    > >
    > > mad_agent_priv->agent.hi_tid = atomic_inc_return(&ib_mad_client_id) & mad_agent_priv->ib_dev->tid_mask;
    > >
    > > And have the driver set tid_mask to 3 bytes of 0xFF
    >
    > The issue is that some of the mad agents are long-lived, so you will
    > wrap and use the same TID twice.

    We already have that problem, and using ida is problematic because we
    need to maximize the time between TID re-use, which ida isn't doing.

    Preventing re-use seems like a seperate issue from limiting the range
    to be compatible with mlx4.

    Jason

    \
     
     \ /
      Last update: 2018-05-29 18:41    [W:4.026 / U:1.180 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site