A single dw_pcie entity can't be a root complex and an endpoint at
the same time.
We can use this to reduce the size of dw_pcie by 80, from 280 to 200
bytes (on x32, guess more on x64), by putting the related embedded
structures (struct pcie_port and struct dw_pcie_ep) into a union.
Signed-off-by: Alexander Lobakin <[email protected]>
---
drivers/pci/controller/dwc/pcie-designware.h | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index 7247c8b01f04..ca8aeba548ab 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -266,8 +266,10 @@ struct dw_pcie {
size_t atu_size;
u32 num_ib_windows;
u32 num_ob_windows;
- struct pcie_port pp;
- struct dw_pcie_ep ep;
+ union {
+ struct pcie_port pp;
+ struct dw_pcie_ep ep;
+ };
const struct dw_pcie_ops *ops;
unsigned int version;
int num_lanes;
--
2.30.2
Hi Alexander,
Thank you for sending the patch over!
> A single dw_pcie entity can't be a root complex and an endpoint at
> the same time.
Nice catch!
A small nitpick: this would be Root Complex and Endpoint, as it's
customary to capitalise these.
Also, if you could capitalise the subject line - it could also perhaps
be simplified to something like, for example:
Optimize struct dw_pcie to reduce its size
Feel free to ignore both suggestions, as these are just nitpicks.
> We can use this to reduce the size of dw_pcie by 80, from 280 to 200
> bytes (on x32, guess more on x64), by putting the related embedded
> structures (struct pcie_port and struct dw_pcie_ep) into a union.
[...]
> - struct pcie_port pp;
> - struct dw_pcie_ep ep;
> + union {
> + struct pcie_port pp;
> + struct dw_pcie_ep ep;
> + };
[...]
How did you measure the difference? Often, people include pahole output
for the "before" and "after", so to speak, to showcase the difference
and/or improvement. Do you have something like that handy?
Krzysztof
From: Krzysztof Wilczyński <[email protected]>
Date: Wed, 24 Mar 2021 02:31:42 +0100
> Hi Alexander,
Hi!
> Thank you for sending the patch over!
>
> > A single dw_pcie entity can't be a root complex and an endpoint at
> > the same time.
>
> Nice catch!
>
> A small nitpick: this would be Root Complex and Endpoint, as it's
> customary to capitalise these.
>
> Also, if you could capitalise the subject line - it could also perhaps
> be simplified to something like, for example:
>
> Optimize struct dw_pcie to reduce its size
>
> Feel free to ignore both suggestions, as these are just nitpicks.
They are both correct, so I can send a v2 if this one wont't be
picked to the tree, let's say, this week.
> > We can use this to reduce the size of dw_pcie by 80, from 280 to 200
> > bytes (on x32, guess more on x64), by putting the related embedded
> > structures (struct pcie_port and struct dw_pcie_ep) into a union.
>
> [...]
> > - struct pcie_port pp;
> > - struct dw_pcie_ep ep;
> > + union {
> > + struct pcie_port pp;
> > + struct dw_pcie_ep ep;
> > + };
> [...]
>
> How did you measure the difference? Often, people include pahole output
> for the "before" and "after", so to speak, to showcase the difference
> and/or improvement. Do you have something like that handy?
I didn't use pahole to measure the difference, just printed sizeofs
for the structures "before" and "after". But I can get pahole's
output and include it in v2 to make commit message more useful.
> Krzysztof
Thanks!
Al